Add support for Repository.describe(...).

docs/repository.rst

@@ -71,3 +71,4 @@ Below there are some general attributes and methods:
 .. automethod:: pygit2.Repository.state_cleanup
 .. automethod:: pygit2.Repository.write_archive
 .. automethod:: pygit2.Repository.ahead_behind
+.. automethod:: pygit2.Repository.describe

pygit2/decl.h

@@ -756,6 +756,47 @@ int git_merge_trees(git_index **out, git_repository *repo, const git_tree *ances
 int git_merge_file_from_index(git_merge_file_result *out, git_repository *repo, const git_index_entry *ancestor, const git_index_entry *ours, const git_index_entry *theirs, const git_merge_file_options *opts);
 void git_merge_file_result_free(git_merge_file_result *result);
 
+/*
+ * Describe
+ */
+
+typedef enum {
+	GIT_DESCRIBE_DEFAULT,
+	GIT_DESCRIBE_TAGS,
+	GIT_DESCRIBE_ALL,
+} git_describe_strategy_t;
+
+typedef struct git_describe_options {
+	unsigned int version;
+	unsigned int max_candidates_tags;
+	unsigned int describe_strategy;
+	const char *pattern;
+	int only_follow_first_parent;
+	int show_commit_oid_as_fallback;
+} git_describe_options;
+
+#define GIT_DESCRIBE_OPTIONS_VERSION ...
+
+int git_describe_init_options(git_describe_options *opts, unsigned int version);
+
+typedef struct {
+	unsigned int version;
+	unsigned int abbreviated_size;
+	int always_use_long_format;
+	const char *dirty_suffix;
+} git_describe_format_options;
+
+#define GIT_DESCRIBE_FORMAT_OPTIONS_VERSION ...
+
+int git_describe_init_format_options(git_describe_format_options *opts, unsigned int version);
+
+typedef ... git_describe_result;
+
+int git_describe_commit(git_describe_result **result, git_object *committish, git_describe_options *opts);
+int git_describe_workdir(git_describe_result **out, git_repository *repo, git_describe_options *opts);
+int git_describe_format(git_buf *out, const git_describe_result *result, const git_describe_format_options *opts);
+void git_describe_result_free(git_describe_result *result);
+
 #define GIT_ATTR_CHECK_FILE_THEN_INDEX ...
 #define GIT_ATTR_CHECK_INDEX_THEN_FILE ...
 #define GIT_ATTR_CHECK_INDEX_ONLY      ...

pygit2/repository.py

@@ -637,6 +637,100 @@ def merge_trees(self, ancestor, ours, theirs, favor='normal'):
 
         return Index.from_c(self, cindex)
 
+    #
+    # Describe
+    #
+    def describe(self, committish=None, max_candidates_tags=None,
+                 describe_strategy=None, pattern=None,
+                 only_follow_first_parent=None,
+                 show_commit_oid_as_fallback=None, abbreviated_size=None,
+                 always_use_long_format=None, dirty_suffix=None):
+        """Describe a commit-ish or the current working tree.
+
+        :param committish: Commit-ish object or object name to describe, or
+            `None` to describe the current working tree.
+        :type committish: `str`, :class:`~.Reference`, or :class:`~.Commit`
+
+        :param int max_candidates_tags: The number of candidate tags to
+            consider. Increasing above 10 will take slightly longer but may
+            produce a more accurate result. A value of 0 will cause only exact
+            matches to be output.
+        :param int describe_strategy: A GIT_DESCRIBE_* constant.
+        :param str pattern: Only consider tags matching the given `glob(7)`
+            pattern, excluding the "refs/tags/" prefix.
+        :param bool only_follow_first_parent: Follow only the first parent
+            commit upon seeing a merge commit.
+        :param bool show_commit_oid_as_fallback: Show uniquely abbreviated
+            commit object as fallback.
+        :param int abbreviated_size: The minimum number of hexadecimal digits
+            to show for abbreviated object names. A value of 0 will suppress
+            long format, only showing the closest tag.
+        :param bool always_use_long_format: Always output the long format (the
+            nearest tag, the number of commits, and the abbrevated commit name)
+            even when the committish matches a tag.
+        :param str dirty_suffix: A string to append if the working tree is
+            dirty.
+
+        :returns: The description.
+        :rtype: `str`
+
+        Example::
+
+            repo.describe(pattern='public/*', dirty_suffix='-dirty')
+        """
+
+        options = ffi.new('git_describe_options *')
+        C.git_describe_init_options(options, C.GIT_DESCRIBE_OPTIONS_VERSION)
+
+        if max_candidates_tags is not None:
+            options.max_candidates_tags = max_candidates_tags
+        if describe_strategy is not None:
+            options.describe_strategy = describe_strategy
+        if pattern:
+            options.pattern = ffi.new('char[]', to_bytes(pattern))
+        if only_follow_first_parent is not None:
+            options.only_follow_first_parent = only_follow_first_parent
+        if show_commit_oid_as_fallback is not None:
+            options.show_commit_oid_as_fallback = show_commit_oid_as_fallback
+
+        result = ffi.new('git_describe_result **')
+        if committish:
+            if is_string(committish):
+                committish = self.revparse_single(committish)
+
+            commit = committish.peel(Commit)
+
+            cptr = ffi.new('git_object **')
+            ffi.buffer(cptr)[:] = commit._pointer[:]
+
+            err = C.git_describe_commit(result, cptr[0], options)
+        else:
+            err = C.git_describe_workdir(result, self._repo, options)
+        check_error(err)
+
+        try:
+            format_options = ffi.new('git_describe_format_options *')
+            C.git_describe_init_format_options(format_options, C.GIT_DESCRIBE_FORMAT_OPTIONS_VERSION)
+
+            if abbreviated_size is not None:
+                format_options.abbreviated_size = abbreviated_size
+            if always_use_long_format is not None:
+                format_options.always_use_long_format = always_use_long_format
+            if dirty_suffix:
+                format_options.dirty_suffix = ffi.new('char[]', to_bytes(dirty_suffix))
+
+            buf = ffi.new('git_buf *', (ffi.NULL, 0))
+
+            err = C.git_describe_format(buf, result[0], format_options)
+            check_error(err)
+
+            try:
+                return ffi.string(buf.ptr).decode('utf-8')
+            finally:
+                C.git_buf_free(buf)
+        finally:
+            C.git_describe_result_free(result[0])
+
     #
     # Utility for writing a tree into an archive
     #

src/pygit2.c

@@ -381,6 +381,11 @@ moduleinit(PyObject* m)
     ADD_CONSTANT_INT(m, GIT_MERGE_ANALYSIS_FASTFORWARD)
     ADD_CONSTANT_INT(m, GIT_MERGE_ANALYSIS_UNBORN)
 
+    /* Describe */
+    ADD_CONSTANT_INT(m, GIT_DESCRIBE_DEFAULT);
+    ADD_CONSTANT_INT(m, GIT_DESCRIBE_TAGS);
+    ADD_CONSTANT_INT(m, GIT_DESCRIBE_ALL);
+
     /* Global initialization of libgit2 */
     git_libgit2_init();
 

test/test_describe.py

@@ -0,0 +1,106 @@
+# -*- coding: UTF-8 -*-
+#
+# Copyright 2010-2015 The pygit2 contributors
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License, version 2,
+# as published by the Free Software Foundation.
+#
+# In addition to the permissions in the GNU General Public License,
+# the authors give you unlimited permission to link the compiled
+# version of this file into combinations with other programs,
+# and to distribute those combinations without any restriction
+# coming from the use of this file.  (The General Public License
+# restrictions do apply in other respects; for example, they cover
+# modification of the file, and distribution when not linked into
+# a combined executable.)
+#
+# This file is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING.  If not, write to
+# the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+# Boston, MA 02110-1301, USA.
+
+"""Tests for describing commits."""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+import unittest
+
+from pygit2 import GIT_DESCRIBE_DEFAULT, GIT_DESCRIBE_TAGS, GIT_DESCRIBE_ALL
+import pygit2
+from . import utils
+
+
+def add_tag(repo, name, target):
+    message = 'Example tag.\n'
+    tagger = pygit2.Signature('John Doe', 'jdoe@example.com', 12347, 0)
+
+    sha = repo.create_tag(name, target, pygit2.GIT_OBJ_COMMIT, tagger, message)
+    return sha
+
+
+class DescribeTest(utils.RepoTestCase):
+
+    def test_describe(self):
+        add_tag(self.repo, 'thetag', '4ec4389a8068641da2d6578db0419484972284c8')
+        self.assertEqual('thetag-2-g2be5719', self.repo.describe())
+
+    def test_describe_without_ref(self):
+        self.assertRaises(pygit2.GitError, self.repo.describe)
+
+    def test_describe_default_oid(self):
+        self.assertEqual('2be5719', self.repo.describe(show_commit_oid_as_fallback=True))
+
+    def test_describe_strategies(self):
+        self.assertEqual('heads/master', self.repo.describe(describe_strategy=GIT_DESCRIBE_ALL))
+
+        self.repo.create_reference('refs/tags/thetag', '4ec4389a8068641da2d6578db0419484972284c8')
+        self.assertRaises(KeyError, self.repo.describe)
+        self.assertEqual('thetag-2-g2be5719', self.repo.describe(describe_strategy=GIT_DESCRIBE_TAGS))
+
+    def test_describe_pattern(self):
+        add_tag(self.repo, 'private/tag1', '5ebeeebb320790caf276b9fc8b24546d63316533')
+        add_tag(self.repo, 'public/tag2', '4ec4389a8068641da2d6578db0419484972284c8')
+
+        self.assertEqual('public/tag2-2-g2be5719', self.repo.describe(pattern='public/*'))
+
+    def test_describe_committish(self):
+        add_tag(self.repo, 'thetag', 'acecd5ea2924a4b900e7e149496e1f4b57976e51')
+        self.assertEqual('thetag-4-g2be5719', self.repo.describe(committish='HEAD'))
+        self.assertEqual('thetag-1-g5ebeeeb', self.repo.describe(committish='HEAD^'))
+
+        self.assertEqual('thetag-4-g2be5719', self.repo.describe(committish=self.repo.head))
+
+        self.assertEqual('thetag-1-g6aaa262', self.repo.describe(committish='6aaa262e655dd54252e5813c8e5acd7780ed097d'))
+        self.assertEqual('thetag-1-g6aaa262', self.repo.describe(committish='6aaa262'))
+
+    def test_describe_follows_first_branch_only(self):
+        add_tag(self.repo, 'thetag', '4ec4389a8068641da2d6578db0419484972284c8')
+        self.assertRaises(KeyError, self.repo.describe, only_follow_first_parent=True)
+
+    def test_describe_abbreviated_size(self):
+        add_tag(self.repo, 'thetag', '4ec4389a8068641da2d6578db0419484972284c8')
+        self.assertEqual('thetag-2-g2be5719152d4f82c', self.repo.describe(abbreviated_size=16))
+        self.assertEqual('thetag', self.repo.describe(abbreviated_size=0))
+
+    def test_describe_long_format(self):
+        add_tag(self.repo, 'thetag', '2be5719152d4f82c7302b1c0932d8e5f0a4a0e98')
+        self.assertEqual('thetag-0-g2be5719', self.repo.describe(always_use_long_format=True))
+
+
+class DescribeDirtyWorkdirTest(utils.DirtyRepoTestCase):
+
+    def setUp(self):
+        super(utils.DirtyRepoTestCase, self).setUp()
+        add_tag(self.repo, 'thetag', 'a763aa560953e7cfb87ccbc2f536d665aa4dff22')
+
+    def test_describe(self):
+        self.assertEqual('thetag', self.repo.describe())
+
+    def test_describe_with_dirty_suffix(self):
+        self.assertEqual('thetag-dirty', self.repo.describe(dirty_suffix='-dirty'))