[[tags: egg]]

== git

[[toc:]]

=== Description

Bindings to the [[http://libgit2.github.com|libgit2]] library.

This library requires libgit2 0.20.0 and Chicken 4.7 or newer.

The source for this egg is available at [[https://bitbucket.org/evhan/chicken-git]].

=== Documentation

{{git}} provides an interface for reading & manipulating git repositories.
The library is split into two modules, {{git}} and {{git-lolevel}}:

* {{git-lolevel}} is essentially just the libgit2 API, thinly wrapped. Most of
  the function signatures remain the same, with a few exceptions: 

** Structures & pointers that would go on the stack are allocated
automatically.

** Return values are checked where appropriate, signaling an exception of type
{{git}} when negative.

** Pointer arrays are converted to rest arguments.

* {{git}} is a higher-level interface around {{git-lolevel}}, providing
  record types for each libgit2 structure.

The following documentation applies to the {{git}} module.

=== Usage

  (use git) ; or...
  (use git-lolevel)

It's not recommended to mix the two without prefixing one or the other's
imports, as the two libraries share many identifiers.

=== API

==== Repository

<record>repository</record>
<procedure>(repository? obj) => boolean</procedure>

A {{repository}} corresponds to an on-disk Git repository.

<procedure>(create-repository [path [bare]]) => repository</procedure>

Creates & returns a new repository at the given {{path}}, or the value of
{{current-directory}} if no path is given. If {{bare}} is given and not {{#f}},
the repository will be created without a working directory. An error is
signaled if the path is invalid or the repository cannot be created.

<procedure>(repository-open [path]) => repository</procedure>

Opens the Git repository indicated by {{path}}, or the value of
{{current-directory}} if no {{path}} is given. {{path}} may point to a bare
repository, a working directory containing a ".git" directory, or a ".git"
directory directly.

<procedure>(repository-path repository) => string</procedure>

Returns the absolute path to the given {{repository}}'s Git directory,
either the topmost directory in the project (if the repository is bare)
or the ".git" subdirectory.

<procedure>(repository-working-directory repository) => (or string false)</procedure>

Returns the absolute path to the given {{repository}}'s working directory,
or {{#f}} if the repository is bare.

<procedure>(repository-ref repository ref) => (or object false)</procedure>

Looks up a Git object in the given {{repository}}. {{ref}} may be a SHA1 string,
{{oid}}, {{reference}}, {{blob}}, {{commit}}, {{tag}} or {{tree}}. The returned
object will be of type {{blob}}, {{commit}}, {{tag}} or {{tree}}, or {{#f}} if
no object matching the given {{ref}} is found.

<procedure>(repository-empty? repository) => boolean</procedure>
<procedure>(repository-bare? repositoy) => boolean</procedure>

Returns a boolean indicating whether the given {{repository}} is empty
(contains no commits) or bare (an exposed git directory without a working
directory).

<procedure>(repository-head-orphan? repositoy) => boolean</procedure>
<procedure>(repository-head-detached? repositoy) => boolean</procedure>
<procedure>(repository-head-unborn? repositoy) => boolean</procedure>

Returns a boolean indicating whether the given repository's {{HEAD}} (a
symbolic reference) is orphaned (unreferenced under the refs namespace),
detached (refering to a commit rather than a branch), or has yet to be
created, respectively.

==== OID

<record>oid</record>
<procedure>(oid? obj) => boolean</procedure>

An {{oid}} is a unique reference to a Git object, corresponding to a
40-character SHA1 object name.

<procedure>(string->oid string) => oid</procedure>

Creates an {{oid}} from the given string, which should be a 40-character SHA1
hash. An error is signaled if the string is not a valid hash.

<procedure>(oid->string oid [length]) => string</procedure>

Returns the string representation of the given {{oid}}. The optional integer
{{length}} specifies the length of the returned string, up to 40 characters.

<procedure>(oid->path oid) => string</procedure>

Returns the string representation of the given {{oid}} in the form "xx/...",
where "xx" is the first two characters of the SHA1 and "..." is the remainder.

<procedure>(oid=? oid1 oid2) => boolean</procedure>

Indicates whether the two {{oid}}s are the equivalent.

==== Revspec

<procedure>(parse-revision-specification string) => (values object object)</procedure>

Attempts to parse a string as a Git revision specification, returning
two values:

* If {{string}} specifies a range of revisions, the start & end
  {{commit}} objects.
* If {{string}} specifies a single revision, the {{commit}} object and
  {{#f}}.
* If {{string}} is invalid or fails to match a revision, {{#f}} for both
  values.

For more information about specifying revisions, see
[[http://git-scm.com/docs/git-rev-parse.html#_specifying_revisions]].

==== Reference

<record>reference</record>
<procedure>(reference? obj) => boolean</procedure>

A {{reference}} is a direct or indirect pointer to a Git commit object. A
repository's {{HEAD}} is a common example: it is a symbolic reference,
referring to the immediate reference {{"refs/heads/master"}}, which in turn
points at a {{commit}}.

<procedure>(reference repository ref) => reference</procedure>

Returns the {{reference}} specified by the given string {{ref}} from the
{{repository}}. {{ref}} must be a string referring to a valid reference, such
as {{HEAD}}, {{"ref/heads/master"}}, or {{"refs/tags/v0.1.0"}}. An error is
signalled if the reference doesn't exists.

<procedure>(reference-name reference) => string</procedure>

Returns the name of the given {{reference}}.

<procedure>(reference-type reference) => symbol</procedure>

Returns the type symbol of the given {{reference}}, which will be either
{{oid}} or {{symbolic}}.

<procedure>(reference-remote? reference) => boolean</procedure>
<procedure>(reference-branch? reference) => boolean</procedure>
<procedure>(reference-tag? reference) => boolean</procedure>

These procedures return boolean values indicating whether the given
reference is a {{remote}}, {{branch}}, or {{tag}}-type reference,
respectively.

<procedure>(references-fold kons knil repository [glob]) => object</procedure>

Folds over the given {{repository}}'s references in unspecified order.

An optional {{glob}} pattern string may be used to filter the references
returned. If given, it will be matched in "glob" style where a {{#\?}}
matches any letter, a {{#\*}} matches any sequence of letters, and
square brackets match a range of characters (such as "[0-9]" for
digits). If no {{glob}} is given, all references will be provided to
{{kons}}.

<procedure>(references repository [type]) => (list-of reference)</procedure>

Returns a list of all references in the given {{repository}}. A type
symbol may be given to filter the references, as in {{references-fold}}.
The order of the resulting list is unspecified.

<procedure>(repository-head repository) => (or reference false)</procedure>

Returns a reference to this repository's HEAD (resolved to an OID), of
{{#f}} if it doesn't exist.

<procedure>(reference-resolve reference) => reference</procedure>

Recursively dereferences the given (possibly symbolic) {{reference}},
returning a new non-symbolic {{reference}} pointing refering directly to
an {{oid}}.

<procedure>(reference-target reference) => oid</procedure>

Returns the {{oid}} of the object which the given {{reference}} refers.
Symbolic references are peeled until a non-symbolic reference is found,
as with {{reference-resolve}}.

<procedure>(reference-rename reference name [force]) => reference</procedure>
<procedure>(reference-target-set! reference target) => void</procedure>

{{reference-rename}} changes the name of the given {{reference}} to the
string {{name}} and returns the newly-updated {{reference}}. If
{{force}} is given and nonfalse, any previously-existing {{reference}}
of the given {{name}} will be overwritten.

{{reference-target-set!}} updates a {{reference}} to refer to the given
{{target}}. If {{reference}} is an immediate reference (referring to an object
ID), {{target}} must be an {{oid}}, {{commit}}, or SHA1 string. If
{{reference}} is symbolic, {{target}} must be a {{reference}} or reference
name. It is an error to assign a symbolic reference an OID target and
vice-versa.

On success, the on-disk repository is updated immediately.

<procedure>(create-reference repository #!key name target [symbolic] [force]) => reference</procedure>

Creates & returns a new reference in the given {{repository}} for the specified
{{name}} and {{target}}. If {{symbolic}} is given and not {{#f}}, the created
reference will be so, and {{target}} must be a reference name or {{reference}}.
Otherwise, {{target}} must be a SHA1 string, {{oid}}, {{commit}} or
{{reference}} to a {{commit}}. If a reference of the given {{name}} exists and
{{force}} is not given or {{#f}}, an error is signalled. Otherwise, creation
is forced and the old reference will be overwritten.

On success, the on-disk repository is updated immediately.

<procedure>(reference-delete reference) => void</procedure>

Deletes the given {{reference}} from its repository.

On success, the on-disk repository is updated immediately.

==== Branch

<procedure>(create-branch repository name target [force]) => reference</procedure>

Creates a new branch in the given {{repository}} of the given {{name}} and
{{target}} and returns a {{reference}} to the new branch. {{target}} must be a
{{commit}} or {{tag}} belonging to the repository. If a branch of the given
{{name}} exists and {{force}} is not given or {{#f}}, an error is signalled.
Otherwise, creation is forced and the old branch is be overwritten.

On success, the on-disk repository is updated immediately.

<procedure>(branch repository name [type]) => (or reference false)</procedure>

Retrieves a {{reference}} to the branch of the given {{name}} from the
repository. {{name}} should be a string naming a branch without a
leading reference namespace such as "refs/heads/" or "refs/remotes". An
error is signaled if no such branch exists.

A {{type}} symbol may be given, either {{local}} or {{remote}}, to
specify what type of branch should be looked up; by default, {{local}}
is used.

<procedure>(branches-fold kons knil repository [type]) => object</procedure>

Folds over the given {{repository}}'s branches.

A {{type}} symbol may be given, either {{local}}, {{remote}}, or
{{all}}, to specify what type of branches should be listed; by default,
{{all}} is used.

<procedure>(branches repository [type]) => (list-of reference)</procedure>

Returns a list {{reference}} objects for each branch in the given
{{repository}}. A type symbol may be given to filter the branches, as in
{{branches-fold}}. The order of the resulting list is unspecified.

<procedure>(branch-head? reference) => boolean</procedure>

Determines whether the given branch {{reference}} is its repository's
current {{HEAD}}.

<procedure>(branch-name reference) => string</procedure>

Returns the name of the given branch {{reference}}. This is similar to
{{reference-name}}, but the leading reference namespace (e.g.
"refs/heads") is omitted.

<procedure>(branch-rename reference name [force]) => reference</procedure>

Renames the given branch {{reference}} to {{name}}, which should be a
string. If {{force}} is given and not false, any existing branch with
the given name will be overwritten. A new, renamed {{reference}} is
returned.

On success, the on-disk repository is updated immediately.

<procedure>(branch-delete reference) => void</procedure>

Deletes the given branch {{reference}} from its repository.

On success, the on-disk repository is updated immediately.

==== Generic Procedures

These procedures can be used on any objects of the four main Git object
types: {{commit}}, {{tree}}, {{tag}} and {{blob}}.

<procedure>(object-id object) => oid</procedure>

Returns the {{oid}} of the given object, which must be a {{commit}},
{{tree}}, {{tag}} or {{blob}}.

<procedure>(object-sha object [length]) => string</procedure>

Returns the SHA1 identifier corresponding to the given object, which may be a
{{commit}}, {{tree}}, {{tag}} {{blob}}, {{reference}}, {{oid}} or {{string}}.

<procedure>(object-type object) => (or symbol false)</procedure>

Returns a symbol specifying the type of the given object, which must be
a {{commit}}, {{tree}}, {{tag}} or {{blob}}. {{#f}} is returned if the
object's type cannot be determined.

<procedure>(object=? object1 object2) => boolean</procedure>

Indicates whether the two Git objects represent the same thing (judging
by their respective {{oid}}s). Each object should be of type {{commit}},
{{tree}}, {{tag}} or {{blob}}.

==== Blob

<record>blob</record>
<procedure>(blob? obj) => boolean</procedure>

A {{blob}} corresponds to Git's Blob object type. It represents a chunk
of data, generally a file.

Beware name collisions with CHICKEN's built-in {{blob}} data type.

<procedure>(blob repository ref) => blob</procedure>

Returns the {{blob}} specified by the given {{ref}} from the repository.
{{ref}} may be a SHA1 string, {{oid}}, or {{blob}}. An error is signaled if
no such {{blob}} exists.

<procedure>(blob-id commit) => oid</procedure>

Returns the {{oid}} of the given {{blob}}.

<procedure>(blob-content blob) => blob</procedure>

Returns a blob (of the CHICKEN built-in type) of the contents of the
given {{blob}} (of the Git object type).

<procedure>(blob-length blob) => int</procedure>

Returns the size in bytes of the given {{blob}}.

<procedure>(blob-binary? blob) => boolean</procedure>

Indicates whether the given {{blob}} is (likely to be) a binary chunk
or not.

<procedure>(create-blob repository source) => blob</procedure>

Creates a new {{blob}} in the given {{repository}}.

{{source}} is the data source for the {{blob}}, and may be a blob (of
the CHICKEN built-in type) or a pathname string indicating a file on the
local disk or, if such a file isn't present, a file relative to the
repository's working directory.

On success, the on-disk repository is updated immediately.

==== Commit

<record>commit</record>
<procedure>(commit? obj) => boolean</procedure>

A {{commit}} corresponds to Git's commit object type.

<procedure>(commit repository ref) => commit</procedure>

Returns the {{commit}} specified by the given {{ref}} from the repository.
{{ref}} may be a SHA1 string, {{oid}}, {{reference}} or {{commit}}. An error
is signaled if no such {{commit}} exists.

<procedure>(commits-fold kons knil repository #!key [initial] [hide] [sort]) => object</procedure>

Folds over the given {{repository}}'s commits. If an {{initial}}
{{commit}} or SHA1 is given, only commits that are ancestors of that
revision will be returned. If a list of revisions to {{hide}} is given,
they and their ancestors will be ignored. If a {{sort}} order is
specified, commits will be collected in the given order; this sort order
must be one of the symbols {{none}}, {{topo}}, {{time}} or {{reverse}},
or a list of such symbols.

<procedure>(commits repository #!rest args) => (list-of commit)</procedure>

Returns a list of the {{commit}}s in the given {{repository}}. {{args}}
follows the {{#!key}} arguments specification for {{commits-fold}}. The
order of the resulting list is opposite that of a call to
{{commits-fold}} with the same arguments.

<procedure>(commit-id commit) => oid</procedure>

Returns the {{oid}} for the given {{commit}}.

<procedure>(commit-time commit) => int</procedure>
<procedure>(commit-time-offset commit) => int</procedure>

{{commit-time}} and {{commit-time-offset}} return the timestamp of the given
{{commit}} and its UTC offset in minutes, respectively.

<procedure>(commit-message commit) => string</procedure>
<procedure>(commit-message-encoding commit) => string</procedure>

Returns the full commit message or message encoding for the given
{{commit}}.

<procedure>(commit-header commit) => string</procedure>

Returns a string header for the given {{commit}}, which is a textual
display of its author, committer, tree and parent commit.

<procedure>(commit-tree commit) => tree</procedure>
<procedure>(commit-tree-id commit) => oid</procedure>

Return the {{tree}} associated with the given {{commit}} and its {{oid}},
respectively.

<procedure>(commit-author commit) => signature</procedure>
<procedure>(commit-committer commit) => signature</procedure>

{{commit-author}} and {{commit-committer}} return the given {{commit}}'s
respective {{signature}}s.

<procedure>(commit-parentcount commit) => int</procedure>
<procedure>(commit-parent commit [n]) => (or commit false)</procedure>
<procedure>(commit-parent-id commit [n]) => (or oid false)</procedure>
<procedure>(commit-parents commit) => (list-of commit)</procedure>
<procedure>(commit-ancestor commit [n]) => (or commit false)</procedure>

{{commit-parentcount}} returns the number of parents of the given
{{commit}}.

{{commit-parent}} returns the {{n}}th parent of the given {{commit}}, or
the first parent if no {{n}} is given. If the {{commit}} has no parent,
{{#f}} is returned.

{{commit-parent-id}} is as {{commit-parent}}, but it returns the {{oid}}
of the given {{commit}}'s parent without first reading the parent commit
from the repository.

{{commit-parents}} returns the possibly-empty list of all parents of the
given {{commit}}. The order of this list is unspecified.

{{commit-ancestor}} returns the {{n}}th ancestor of the given commit, or
{{#f}} is no such ancestor exists. {{n}} defaults to {{1}}, meaning the
{{commit}}'s first parent (making {{(commit-ancestor c 1)}} equivalent
to {{(commit-parent c)}}).

<procedure>(create-commit repository #!key message author [committer] [tree] [parents] [reference]) => commit</procedure>

Creates & returns a new commit in the given {{repository}}. The string
{{message}} will be used as the commit's message and {{tree}} will be
the file tree of the commit. If no {{tree}} is given, the current state
of the repository's {{index}} is used. {{parents}} may be be a (possibly
empty) list of commits to be used as this commit's ancestors. {{author}}
and {{committer}} should be signatures; if {{committer}} is not given,
{{author}} will be used for both. {{reference}}, if given and not
{{#f}}, should be the {{reference}} or name of a {{reference}} that will
be updated to point to the newly-created commit.

Note that if no {{reference}} is given, the commit will be created in
Git's database but will not be reflected in any of the repository's
branches. To update the the working branch with the new commit, for
example, use {{"HEAD"}}.

On success, the on-disk repository is updated immediately.

<procedure>(merge-base repository commit1 commit2) => commit</procedure>

Returns the nearest common ancestor for the given commits. {{commit1}} and
{{commit2}} may be {{commit}}s, commit {{oid}}s, or SHA1 hashes.

==== Tag

<record>tag</record>
<procedure>(tag? obj) => boolean</procedure>

A {{tag}} corresponds to Git's Tag object type, which is a way to mark a
specific object as special in some way.

<procedure>(tag repository ref) => tag</procedure>

Creates & returns the {{tag}} specified by the given {{ref}} from the
repository. {{ref}} may be a SHA1 string, {{oid}}, or {{tag}}. An error is
signaled if no such {{tag}} exists.

<procedure>(tags-fold kons knil repository) => object</procedure>

Folds over the given repository's {{tag}}s in unspecified order.

<procedure>(tags repository) => (list-of tag)</procedure>

Returns a list of all tags in the given {{repository}}. The order of
the resulting list is unspecified.

<procedure>(tag-id tag) => oid</procedure>

Returns the {{oid}} for the given {{tag}}.

<procedure>(tag-type tag) => symbol</procedure>

Returns the object type symbol of the target of the given {{tag}}, which will
be one of {{commit}}, {{tree}}, {{blob}}, or {{tag}}.

<procedure>(tag-name tag) => string</procedure>
<procedure>(tag-message tag) => string</procedure>

Return the name or message of the given {{tag}}.

<procedure>(tag-tagger tag) => signature</procedure>

Returns the {{signature}} of the {{tag}}'s creator.

<procedure>(tag-peel tag) => object</procedure>

Recursively dereferences the given {{tag}} until a non-tag object to
which it refers is found (and returned).

<procedure>(tag-target tag) => object</procedure>
<procedure>(tag-peel tag) => object</procedure>

{{tag-target}} returns the object referred to by {{tag}}, which will be of type
{{commit}}, {{tree}}, {{blob}} or {{tag}}.

Returns the object immediately referred to by {{tag}}, which will be of
type {{commit}}, {{tree}}, {{blob}} or {{tag}}.

<procedure>(tag-delete tag) => void</procedure>

Destroys the given {{tag}}.

On success, the on-disk repository is updated immediately.

<procedure>(create-tag repository #!key target name message tagger [force]) => tag</procedure>

Creates & returns a new tag in the given {{repository}} for the specified
{{name}}, {{message}} and {{target}}. {{name}} and {{message}} must be strings,
{{tagger}} must be a {{signature}},and {{target}} must be a {{commit}},
{{tree}} or {{blob}}. If a tag of the given {{name}} exists and {{force}} is
not given or {{#f}}, an error is signalled.  Otherwise, creation is forced and
the old tag will be overwritten.

On success, the on-disk repository is updated immediately.

==== Tree

<record>tree</record>
<procedure>(tree? obj) => boolean</procedure>

A {{tree}} corresponds to Git's Tree object type, which represents a directory
tree.

<procedure>(tree repository ref) => tree</procedure>

Returns the {{tree}} specified by the given {{ref}} from the repository. {{ref}}
may be a SHA1 string, {{oid}}, or {{tree}}. An error is signaled if no such
{{tree}} exists.

<procedure>(tree-id tree) => oid</procedure>

Returns the {{oid}} for the given {{tree}}.

<procedure>(tree-entrycount tree) => int</procedure>

Returns the number of entries in the given {{tree}}. This count does not
include entries of contained directories.

<procedure>(tree-ref tree key) => (or tree-entry false)</procedure>

Returns a {{tree-entry}} object for the given {{key}} from the tree, or
{{#f}} if no such tree entry is found. {{key}} may be a zero-based
integer index or a pathname string relative to the repository's working
directory.

<procedure>(tree-fold kons knil tree) => object</procedure>

Folds over each path and accompanying {{tree-entry}} in the given
{{tree}} in unspecified order.

Note that {{kons}} should be a function of three arguments; the path to
the current {{tree-entry}} (a string, relative to the repository's working
directory), the current {{tree-entry}}, and the current state of the
fold.

<procedure>(tree-entries tree) => (list-of (pair string tree-entry))</procedure>

Returns an alist of all {{tree-entry}} objects in the given {{tree}},
whose keys are pathname strings indicating each {{tree-entry}}'s
location in the tree and whose values are the {{tree-entry}} objects
themselves. The order of the resulting list is unspecified.

<procedure>(create-tree repository [index]) => tree</procedure>

Creates and returns a new {{tree}} object from the state of the given
{{index}} in the given {{repository}}.

If {{index}} is not given, a fresh {{index}} for the repository is used.
This means the resulting {{tree}} will be identical to that of the
repository's {{HEAD}}.

On success, the new value is written immediately to disk.

==== Tree Entry

<record>tree-entry</record>
<procedure>(tree-entry? obj) => boolean</procedure>

A {{tree-entry}} represents a single node in a {{tree}} object.

<procedure>(tree-entry-id tree-entry) => oid</procedure>

Returns the {{oid}} of the given {{tree-entry}}.

<procedure>(tree-entry-name tree-entry) => string</procedure>

Returns the name of the given {{tree-entry}}.

<procedure>(tree-entry-attributes tree-entry) => int</procedure>

Returns the Unix file attributes of the given {{tree-entry}}.

<procedure>(tree-entry-type tree-entry) => symbol</procedure>

Returns the object type symbol, either {{tree}} or {{blob}}, of the given
{{tree-entry}}.

<procedure>(tree-entry->object [repository] tree-entry) => object</procedure>

Returns an object of type {{tree}} or {{blob}} from the given {{tree-entry}}
and {{repository}}, which must be the owner of the {{tree-entry}}.

If no {{repository}} is given, {{tree-entry->object}} will attempt to
determine the owning repository from the {{tree-entry}}. This is only
possible if the {{tree-entry}} belongs to a {{tree}}; if it belongs to a
{{tree-builder}}, instead, an error will be signaled.

==== Tree Builder

<record>tree-builder</record>
<procedure>(tree-builder? obj) => boolean</procedure>

A tree builder provides a way to construct {{tree}} objects in memory and write
them to a repository, without using an index as an intermediary.

<procedure>(make-tree-builder [tree]) => tree-builder</procedure>

Creates a new {{tree-builder}}. If a {{tree}} is given, it is used as the
constructed tree's initial state. Otherwise, it must be populated manually
using {{tree-builder-insert}}.

<procedure>(tree-builder-insert tree-builder object name attributes) => tree-entry</procedure>

Inserts {{object}} into the {{tree-builder}}'s tree under the given filename
{{name}}. The inserted object must be a {{tree}} or {{blob}}, and will have
the given {{attributes}} (an integer file mode).

<procedure>(tree-builder-ref tree-builder path) => (or tree-entry false)</procedure>

Returns the {{tree-entry}} from the given {{tree-builder}} at {{path}}, which
should be a filename string. If the requested file doesn't exist, {{#f}} is
returned.

<procedure>(tree-builder-remove tree-builder path) => void</procedure>

Removes the object at the given {{path}} from the {{tree-builder}}'s tree.

<procedure>(tree-builder-write repository tree-builder) => tree</procedure>

Writes the {{tree-builder}}'s current state to the given {{repository}},
modifying the on-disk repository on success. The resulting {{tree}} is
returned.

<procedure>(tree-builder-clear tree-builder) => void</procedure>

Removes all objects from the given {{tree-builder}}.

==== Diff

<record>diff</record>
<procedure>(diff? obj) => boolean</procedure>

A {{diff}} is the cumulative difference between two Git {{tree}}s (or
{{tree}}-like objects). It consists of a number of {{diff-delta}}s, each
of which represents the difference in a single file.

<procedure>(diff repository [object1 [object2]]) => diff</procedure>

Returns a {{diff}} between two objects in the {{repository}}.

{{diff}}'s behavior is as follows, given the following arguments:

* {{()}}: diff the repository's index to its working directory
* {{(index)}}: diff the given index to the repository's working directory
* {{(tree)}}: diff the given tree to the repository's working directory
* {{(tree tree)}}: diff the given trees
* {{(tree index)}}: diff the given tree to the given index

<procedure>(diff-fold kons knil diff) => object</procedure>

Folds over the given {{diff}}'s {{diff-delta}}s in unspecified order.

<procedure>(diff-deltas {{diff}}) => (list-of diff-delta)</procedure>

Returns the list of {{diff-delta}}s for all changed files in the given
{{diff}}.

<record>diff-delta</record>
<procedure>(diff-delta-path diff) => string</procedure>
<procedure>(diff-delta-status diff) => symbol</procedure>
<procedure>(diff-delta-old-file diff) => diff-file</procedure>
<procedure>(diff-delta-new-file diff) => diff-file</procedure>
<record>diff-file</record>
<procedure>(diff-file? obj) => boolean</procedure>
<procedure>(diff-file-id diff-file) => oid</procedure>
<procedure>(diff-file-path diff-file) => string</procedure>
<procedure>(diff-file-size diff-file) => integer</procedure>
<procedure>(diff-file-mode diff-file) => integer</procedure>

A {{diff-delta}} is the difference in a single file between two Git {{tree}}s.
Each diff has a path, a status, a pair of {{diff-file}}s for the old and
new files (retrieved by {{diff-old-file}} and {{diff-new-file}},
respectively), and a list of {{diff-hunk}}s representing individual
changes.

Each {{diff-file}} has an {{id}}, {{path}}, {{size}} and {{mode}} (Unix
file attributes).

<procedure>(diff-status diff) => symbol</procedure>

Returns a symbol representing the status of a {{diff}}, which will be
one of the following symbols, or a list of them if the {{diff}}'s file
is in multiple statuses:

    modified
    added
    deleted
    modified
    renamed
    copied
    ignored
    untracked

<procedure>(diff-patch diff n) => patch</procedure>

Returns a {{patch}} for the {{n}}th {{diff-delta}} in the given
{{diff}}.

<procedure>(diff-patches diff) => patch</procedure>

Returns a list of {{patch}}es for all {{diff-delta}}s in the given
{{diff}}.

<procedure>(diff->string diff) => string</procedure>

Returns a string representation of the given {{diff}} as a patch.

This is equivalent to concatenating the string representations of each
{{patch}} given by {{diff-patches}}.

<procedure>(diff-old-file diff) => (or diff-file false)</procedure>
<procedure>(diff-new-file diff) => (or diff-file false)</procedure>

Returns the {{diff-file}} object for the old and new file of the given
{{diff}}, respectively. If the file is added or deleted, {{#f}} will be
returned for the diff's old or new file, respectively.

<procedure>(diff-hunks diff) => (list-of diff-hunk)</procedure>

Returns the list of {{diff-hunk}}s in the given {{diff}}.

<record>diff-hunk</record>
<procedure>(diff-hunk? obj) => boolean</procedure>
<procedure>(diff-hunk-header diff) => string</procedure>
<procedure>(diff-hunk-old-lines diff) => integer</procedure>
<procedure>(diff-hunk-old-start diff) => integer</procedure>
<procedure>(diff-hunk-new-lines diff) => integer</procedure>
<procedure>(diff-hunk-new-start diff) => integer</procedure>

A {{diff-hunk}} represents a group of changes in a diff, with some
surrounding context. Each has a header describing the change, line
counts and start offsets for the old and new versions of the hunk, and a
list of {{diff-line}}s representing each added or deleted range of bytes
in the group of changes.

<procedure>(diff-hunk-lines diff) => (list-of diff-line)</procedure>

<record>diff-line</record>
<procedure>(diff-line? obj) => boolean</procedure>
<procedure>(diff-line-origin diff) => char</procedure>
<procedure>(diff-line-content diff) => string</procedure>
<procedure>(diff-line-num-lines diff) => integer</procedure>
<procedure>(diff-line-old-lineno diff) => integer</procedure>
<procedure>(diff-line-new-lineno diff) => integer</procedure>

A {{diff-line}} is a range of bytes in a {{diff-hunk}} and represents
either an addition, a deletion, or a range that is present in both the
old and new versions of the hunk but is included for context. Which of
these a given {{diff-line}} corresponds to is indicated by its
{{diff-line-origin}}, one of {{#\+}}, {{#\-}} or {{#\space}}.

==== Patch

<record>patch</record>
<procedure>(patch? obj) => boolean</procedure>

A {{patch}} is a textual representation of a {{diff-delta}}.

<procedure>(patch->string patch) => string</procedure>

Returns the string representation of the given {{patch}}.

<procedure>(patch-size patch) => integer</procedure>

Returns the total number of bytes in the patch, including hunk and line
headers and context lines.

<procedure>(patch-stats patch) => (vector-of integer integer integer)</procedure>

Returns a three-element vector containing the number of lines of
context, number of lines added, and number of lines deleted in the
patch.

==== Status

<procedure>(file-status repository path) => symbol</procedure>

Returns the status of the file specified by {{path}} in the given
{{repository}}.

This status will be one of the following symbols, or a list of them if
the file is in multiple statuses:

    current
    index/new
    index/modified
    index/deleted
    worktree/new
    worktree/modified
    worktree/deleted
    ignored

<procedure>(file-statuses-fold kons knil repository) => object</procedure>

Folds over each path and the corresponding file's status in the given
{{repository}}'s working directory in unspecified order.

Note that {{kons}} should be a function of three arguments; the pathname
of the current file (a string, relative to the repository's working
directory), the current status symbol, and the current state of the
fold.

<procedure>(file-statuses repository) => (list-of (pair string symbol))</procedure>

Returns an alist of all file statuses in the given {{repository}}, whose
keys are pathnames to each file and whose values are the status symbols
of those files. The order of the resulting list is unspecified.

<procedure>(file-ignored? repository path) => boolean</procedure>

Returns a boolean indicating whether the given {{path}} in {{repository}} is
ignored by Git or not.

==== Ignore

<procedure>(path-ignored? repository path) => boolean</procedure>

Returns a boolean indicating whether the given {{path}} in
{{repository}} is ignored by Git or not. This is equivalent to
{{file-ignored?}}.

<procedure>(ignore-add! repository glob) => void</procedure>

Adds {{glob}} as an ignore rule to the given {{repository}}. Files
matching this pattern will be ignored for all operations on the
in-memory {{repository}}. Rules added in this way are not be persisted
to the file system.

<procedure>(ignore-clear! repository) => void</procedure>

Removes all ignore rules that have been added to the {{repository}} by
{{ignore-add!}}.

==== Note

<record>note</record>
<procedure>(note? obj) => boolean</procedure>

A {{note}} is a type of reference, stored under the {{refs/notes}}
namespace. It's used to associate some data (accessible via
{{note-message}}) with an object.

<procedure>(note-message note) => string</procedure>
<procedure>(note-id note) => oid</procedure>

{{note-message}} and {{note-id}} return the string content and {{oid}}
of the given {{note}}, respectively.

<procedure>(note repository object [reference]) => note</procedure>

Returns the {{note}} associated with the given {{object}} in the
{{repository}}. {{reference}} may be a string specifying an alternative
notes reference namespace, which defaults to {{"refs/notes/commits"}}.
An error is signaled if no such {{note}} exists.

<procedure>(delete-note repository #!key target author [committer] [reference]) => void</procedure>

Deletes all notes for the given object {{target}} by the given
{{author}} in the {{repository}}. {{author}} and {{committer}} should be a
{{signature}}s, while {{reference}} may specify an alternative notes
reference namespace, which defaults to {{"refs/notes/commits"}}.

On success, the note is removed from disk immediately. An error is
signaled if no such {{note}} exists.

<procedure>(create-note repository #!key message target reference author [committer] [force]) => note</procedure>

Creates & returns a new {{note}} in the given {{repository}} with the
specified {{message}} and {{target}} object. {{author}} and
{{committer}} should be {{signature}}s, while {{reference}} may specify
an alternative notes reference namespace, which defaults to
{{"refs/notes/commits"}}. If {{force}} is given and not {{#f}}, an
existing note for the same {{target}} and {{author}}/{{committer}} will
be overwritten; otherwise, an error will be signaled if such a {{note}}
already exists.

On success, the on-disk repository is updated immediately.

<procedure>(notes-fold kons knil repository [reference]) => object</procedure>

Folds over the given {{repository}}'s notes in unspecified order.

{{reference}} may specify an alternative notes reference namespace,
which defaults to {{"refs/notes/commits"}}.

<procedure>(notes repository [reference]) => (list-of note)</procedure>

Returns a list of all notes in the given {{repository}}. The order of
the resulting list is unspecified.

{{reference}} may specify an alternative notes reference namespace,
which defaults to {{"refs/notes/commits"}}.

==== Index

<record>index</record>
<procedure>(index? obj) => boolean</procedure>

An {{index}} represents the on-disk state of Git's working tree. Changes made
to a given {{index}} exist only in memory until written to disk using
{{index-write}}.

<procedure>(index-open repository-or-path) => index</procedure>

It {{repository-or-path}} is a {{repository}}, {{index-open}} returns
the repository's index. If it's a string, {{index-open}} creates and
returns the index at the given path, signaling an error if such an index
doesn't exist. It is not possible to open the index of a bare
repository, and doing so will result in an exception.

<procedure>(index-entrycount index) => int</procedure>

Returns the total number of index entries entries of the given
{{index}}, respectively. This is essentially a count of all files
tracked by Git in a given repository.

<procedure>(index-read index) => void</procedure>

Updates the given {{index}} to reflect the current state of the on-disk
repository.

<procedure>(index-write index) => void</procedure>

Writes the state of the given {{index}} from memory onto disk, modifying
the repository on success.

<procedure>(index-clear index) => void</procedure>

Removes all enries from a given {{index}}.

<procedure>(index-add index path [stage]) => void</procedure>

Adds a given {{path}}, which must refer to a file relative to the index's
repository, to the {{index}}. If an integer {{stage}} is given, it will be used
as the staging number for the changes.

<procedure>(index-remove index ref) => void</procedure>

Removes an entry from the given {{index}}. {{ref}} may be a file path string or
an zero-based integer index. If no entry is removed, {{#f}} is returned.

<procedure>(index-find index path) => int</procedure>

Returns the zero-based integer index of the file specified by {{path}} in the
given {{index}}, signaling an error if it doesn't exist.

<procedure>(index-ref index key [type]) => (or index-entry false)</procedure>

Returns the {{index-entry}} from the {{index}} for the given {{key}}, which may
be an zero-based integer index or a pathname string, or {{#f}} if no such entry
exists. If a type symbol is given, either {{merged}} (the default behavior) or
{{unmerged}}, the search will be limited to such entries.

==== Index Entry

<record>index-entry</record>
<procedure>(index-entry? obj) => boolean</procedure>

An {{index-entry}} represents a tracked file in Git's working directory,
belonging to an {{index}}.

<procedure>(index-entry-id index-entry) => oid</procedure>

Returns the {{oid}} referring to the given {{index-entry}}.

<procedure>(index-entry-path index-entry) => string</procedure>

Returns the file path of the given {{index-entry}} relative to the owning
repository's working directory.

<procedure>(index-entry-ctime index-entry) => int</procedure>
<procedure>(index-entry-mtime index-entry) => int</procedure>
<procedure>(index-entry-dev index-entry) => int</procedure>
<procedure>(index-entry-ino index-entry) => int</procedure>
<procedure>(index-entry-size index-entry) => int</procedure>
<procedure>(index-entry-stage index-entry) => int</procedure>
<procedure>(index-entry-uid index-entry) => int</procedure>
<procedure>(index-entry-gid index-entry) => int</procedure>
<procedure>(index-entry-mode index-entry) => int</procedure>
<procedure>(index-entry-flags index-entry) => int</procedure>
<procedure>(index-entry-extended index-entry) => int</procedure>

These methods return the file attributes for the given {{index-entry}} as it
exists in its in-memory {{index}}.

==== ODB

<record>odb</record>
<procedure>(odb? obj) => boolean</procedure>

An {{odb}} offers a direct interface to Git's internal object database.

<procedure>(odb-open repository-or-path) => odb</procedure>

It {{repository-or-path}} is a {{repository}}, returns the repository's
object database. If it is a string, creates and returns the object
database at the given path, signaling an error if no such database
exists.

<procedure>(odb-has-object? odb ref) => boolean</procedure>

Determines if the given {{odb}} contains the given object {{ref}}, which should
be a SHA1 string, {{oid}} or Git object of type {{commit}}, {{blob}}, {{tree}}
or {{tag}}.

<procedure>(odb-read odb ref) => odb-object</procedure>

Reads the given object {{ref}} from the database, signaling an error if it
doesn't exist. {{ref}} should be a SHA1 string, {{oid}} or Git object of type
{{commit}}, {{blob}}, {{tree}} or {{tag}}.

<procedure>(odb-write odb data [type]) => oid</procedure>

Writes a given data {{blob}} to the {{odb}}, returning an {{oid}} referring to
the newly-created object. The type of the stored data can be specified by an
optional {{type}} symbol, which defaults to {{blob}}.

<procedure>(odb-hash odb data [type]) => oid</procedure>

Returns an {{oid}} reference for the given data {{blob}} as though it had been
stored to the given {{odb}} but without writing it to disk. The type of the
hashed data can be specified by an optional {{type}} symbol, which defaults to
{{blob}}.

==== ODB Object

<record>odb-object</record>
<procedure>(odb-object? obj) => boolean</procedure>

An {{odb-object}} is a reference to a blob of data in a Git object database.

<procedure>(odb-object-id odb-object) => oid</procedure>

Returns the {{oid}} for the given {{odb-object}}.

<procedure>(odb-object-size odb-object) => int</procedure>

Returns the size of the {{odb-object}}'s data in bytes.

<procedure>(odb-object-type odb-object) => symbol</procedure>

Returns the object type symbol of the given {{odb-object}}.

<procedure>(odb-object-data odb-object) => blob</procedure>

Returns a blob consisting of the {{odb-object}}'s data.

==== Signature

<record>signature</record>
<procedure>(signature? obj) => boolean</procedure>

A signature is a record of the name, email, time and UTC offset of a given Git
object.

<procedure>(make-signature name email [time [offset]]) => signature</procedure>

Returns a new {{signature}} for the given name and email strings. If a
timestamp {{time}} and integer {{offset}} are given, they will be used as the
signature time; otherwise, the current time will be used.

Unlike the {{create-*}} functions, no representation of this signature is
created in the repository; it exists only in memory until associated with a
{{commit}} or {{tag}}.

<procedure>(signature-name signature) => string</procedure>
<procedure>(signature-email signature) => string</procedure>

{{signature-name}} and {{signature-email}} return strings for the
given {{signature}}'s respective fields.

<procedure>(signature-time signature) => int</procedure>
<procedure>(signature-time-offset signature) => int</procedure>

{{signature-time}} and {{signature-time-offset}} return the timestamp of the
given {{signature}} and its UTC offset in minutes, respectively.

==== Checkout

<procedure>(checkout repository [object]) => void</procedure>

{{checkout}} updates files in the working directory and index of the
given {{repository}} to match the state of {{object}}.

If {{object}} is an {{index}}, the {{repository}}'s working directory
will be updated to match the its state.

If {{object}} is a {{commit}}, {{tag}} or {{tree}}, the {{repository}}'s
working directory and index will both be updated to reflect its state.

If {{object}} is omitted or {{#f}}, the {{repository}}'s working
directory and index will both be updated to match the state of the
repository's {{HEAD}}.

Note that {{checkout}} will silently delete untracked files and
overwrite changes to tracked files in the repository's working
directory.

==== Clone

<procedure>(clone url path) => void</procedure>

Clones the remote Git repository specified by {{url}} into the local
pathname {{path}}.

On success, the branch indicated by the {{HEAD}} reference of the remote
repository is checked out as a normal (i.e. non-bare) Git working
directory.

An error is signaled if the clone fails for any reason.

==== Config

<record>config</record>
<procedure>(config? obj) => boolean</procedure>

A {{config}} represents a Git configuration file, associated with either a
repository, the current user, or the system-wide Git installation.

<procedure>(config-path [type]) => string</procedure>

Returns the path to a Git configuration file, if one exists. {{type}}
may be a symbol specifying the type of path to search, either {{user}},
{{system}} or {{xdg}}, to request the path to the configuration for
the current user, the system-wide Git installation, or the configuration
file path specified by the XDG standard (".config/git/config"),
respectively. {{type}} defaults to {{user}}. An error is signalled if
no configuration file is found at the requested location.

<procedure>(config-open [source]) => config</procedure>

Reads the Git configuration file indicated by {{source}}, which may be a
{{repository}}, path, or symbol as expected by {{config-path}}. An
error is signalled if no configuration file is found at the requested location.

<procedure>(config-get config name [type]) => object</procedure>

Returns the value of the property {{name}} in the given {{config}}
object. The value is returned as a string, unless an alternative return
type is specified by the given symbol {{type}}, which should be
{{string}}, {{symbol}}, {{number}} or {{boolean}}. An error is
signaled if the requested property doesn't exist, or if it cannot be
converted to the specified return type.

<procedure>(config-set! config name value) => object</procedure>

Sets the value of the property {{name}} in the given {{config}} object to the
given {{value}}.

On success, the new value is written immediately to disk.

<procedure>(config-unset! config name) => void</procedure>

Deletes the property {{name}} from the given {{config}} object.

On success, the change is written immediately to disk.

=== History

* 0.0.27 - libgit2 0.20.0 ignore API
* 0.0.26 - libgit2 0.20.0 types
* 0.0.25 - libgit2 0.20.0 expanded diff API
* 0.0.24 - libgit2 0.20.0
* 0.0.23 - libgit2 0.19.0 object owner tracking
* 0.0.22 - libgit2 0.19.0 note, clone & revparse bindings
* 0.0.21 - libgit2 0.19.0 fix for repository-ref on 32-bit platforms
* 0.0.20 - libgit2 0.19.0
* 0.0.19 - libgit2 0.18.0 reference & branch API updates
* 0.0.18 - libgit2 0.18.0

=== Author

Evan Hanson

=== License

Copyright (c) 2013-2014, Evan Hanson, 3-Clause BSD License