GitRepository: add format_patch method

A method for generating one patch, with the possibility to filter the
git patch through a python function.

Always generates textual diffs as the 'patch' utility doesn't support
git binary diffs.

Ignore changes to submodules in patch generation as these diffs cannot
be applied by the patch utility when building packages.

TODO: convert all code to use the new format_patch() and get rid of the
format_patches() method.

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>

2 files changed, 71 insertions, 0 deletions

diff --git a/gbp/git/repository.py b/gbp/git/repository.py
index c57f81ff..a1369f14 100644
--- a/gbp/git/repository.py
+++ b/gbp/git/repository.py
@@ -1481,6 +1481,49 @@ class GitRepository(object):
         output, ret = self._git_getoutput('format-patch', options.args)
         return [ line.strip() for line in output ]
 
+    def format_patch(self, commit, output, signature=True, paths=None,
+                     filter_fn=None, filter_args={}):
+        """
+        Create patch of a single commit
+
+        @param commit: commit to create patch from
+        @type commit: C{str}
+        @param output: path/filename of the patch file to be generated
+        @type output: C{str}
+        @param signature: add signature to the end of patch
+        @type signature: C{bool}
+        @param paths: only list commits touching paths
+        @type paths: C{list} of C{str}
+        @return: patch path/filename or None if no patch was generated
+        @param filter_fn: python function for filtering the stdout
+        @type filter_fn: C{function}
+        @param filter_args: arguments to pass to the filter fn
+        @type filter_args: C{dict}
+        @rtype: C{str}
+        """
+        args = GitArgs('-k', '--stdout', '-a', '--ignore-submodules')
+        args.add_cond(not signature, '--no-signature')
+        args.add('%s^!' % commit)
+        if paths:
+            args.add('--', paths)
+
+        try:
+            output_dir = os.path.dirname(output)
+            if output_dir and not os.path.exists(output_dir):
+                os.mkdir(output_dir)
+        except OSError as err:
+            raise GitRepositoryError("Unable to create patch directory" % err)
+
+        with open(output, 'w') as f_out:
+            dummy, stderr, ret = self._git_inout('format-patch', args.args,
+                                                 output_f=f_out,
+                                                 filter_fn=filter_fn,
+                                                 filter_kwargs=filter_args)
+        if os.path.getsize(output) == 0:
+            os.unlink(output)
+            output = None
+        return output
+
     def apply_patch(self, patch, index=True, context=None, strip=None):
         """Apply a patch using git apply"""
         args = []
diff --git a/tests/test_GitRepository.py b/tests/test_GitRepository.py
index 3cacf897..bc9d87a3 100644
--- a/tests/test_GitRepository.py
+++ b/tests/test_GitRepository.py
@@ -430,6 +430,34 @@ def test_get_commit_info():
     defaultdict(<type 'list'>, {'M': ['testfile']})
     """
 
+def test_format_patch():
+    """
+    Test generating of single patch
+
+    Methods tested:
+         - L{gbp.git.GitRepository.format_patch}
+
+    >>> import os
+    >>> import filecmp
+    >>> import gbp.git
+    >>> repo = gbp.git.GitRepository(repo_dir)
+    >>> repo.format_patch("HEAD", "foo.patch", signature=False)
+    'foo.patch'
+    >>> repo.format_patch("HEAD", "foo2.patch", signature=False, paths="testfile")
+    'foo2.patch'
+    >>> repo.format_patch("HEAD", "foo3.patch", signature=False, paths="filenotexists")
+    >>> os.path.getsize("foo.patch") > 300
+    True
+    >>> os.path.getsize("foo2.patch") > 300
+    True
+    >>> filecmp.cmp("foo.patch", "foo2.patch")
+    True
+    >>> os.path.exists("foo3.patch")
+    False
+    >>> os.unlink("foo.patch")
+    >>> os.unlink("foo2.patch")
+    """
+
 def test_diff():
     """
     Test git-diff