patman: Show the base commit and branch

It is helpful to know which commit patches are based on, even if that
commit might not be available to readers. Add a tag for this in the
cover letter.

Also add the local-branch name since that may be useful to the writer.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/func_test.py

@@ -216,6 +216,8 @@ class TestFunctional(unittest.TestCase):
 
         text = self._get_text('test01.txt')
         series = patchstream.get_metadata_for_test(text)
+        series.base_commit = Commit('1a44532')
+        series.branch = 'mybranch'
         cover_fname, args = self._create_patches_for_test(series)
         get_maintainer_script = str(pathlib.Path(__file__).parent.parent.parent
                                     / 'get_maintainer.pl') + ' --norolestats'
@@ -308,6 +310,8 @@ Simon Glass (2):
 --\x20
 2.7.4
 
+base-commit: 1a44532
+branch: mybranch
 '''
         lines = open(cover_fname, encoding='utf-8').read().splitlines()
         self.assertEqual(
@@ -511,12 +515,18 @@ complicated as possible''')
             # Check that it can detect a different branch
             self.assertEqual(3, gitutil.count_commits_to_branch('second'))
             with capture_sys_output() as _:
-                _, cover_fname, patch_files = control.prepare_patches(
+                series, cover_fname, patch_files = control.prepare_patches(
                     col, branch='second', count=-1, start=0, end=0,
                     ignore_binary=False, signoff=True)
             self.assertIsNotNone(cover_fname)
             self.assertEqual(3, len(patch_files))
 
+            cover = tools.read_file(cover_fname, binary=False)
+            lines = cover.splitlines()[-2:]
+            base = repo.lookup_reference('refs/heads/base').target
+            self.assertEqual(f'base-commit: {base}', lines[0])
+            self.assertEqual('branch: second', lines[1])
+
             # Check that it can skip patches at the end
             with capture_sys_output() as _:
                 _, cover_fname, patch_files = control.prepare_patches(
@@ -524,6 +534,13 @@ complicated as possible''')
                     ignore_binary=False, signoff=True)
             self.assertIsNotNone(cover_fname)
             self.assertEqual(2, len(patch_files))
+
+            cover = tools.read_file(cover_fname, binary=False)
+            lines = cover.splitlines()[-2:]
+            base2 = repo.lookup_reference('refs/heads/second')
+            ref = base2.peel(pygit2.GIT_OBJ_COMMIT).parents[0].parents[0].id
+            self.assertEqual(f'base-commit: {ref}', lines[0])
+            self.assertEqual('branch: second', lines[1])
         finally:
             os.chdir(orig_dir)
 

tools/patman/patchstream.py

@@ -755,8 +755,12 @@ def get_metadata(branch, start, count):
     Returns:
         Series: Object containing information about the commits.
     """
-    return get_metadata_for_list(
-        '%s~%d' % (branch if branch else 'HEAD', start), None, count)
+    top = f"{branch if branch else 'HEAD'}~{start}"
+    series = get_metadata_for_list(top, None, count)
+    series.base_commit = commit.Commit(gitutil.get_hash(f'{top}~{count}'))
+    series.branch = branch or gitutil.get_branch()
+    series.top = top
+    return series
 
 def get_metadata_for_test(text):
     """Process metadata from a file containing a git log. Used for tests
@@ -868,4 +872,11 @@ def insert_cover_letter(fname, series, count):
             out = series.MakeChangeLog(None)
             line += '\n' + '\n'.join(out)
         fil.write(line)
+
+    # Insert the base commit and branch
+    if series.base_commit:
+        print(f'base-commit: {series.base_commit.hash}', file=fil)
+    if series.branch:
+        print(f'branch: {series.branch}', file=fil)
+
     fil.close()

tools/patman/series.py

@@ -42,6 +42,8 @@ class Series(dict):
         self.notes = []
         self.changes = {}
         self.allow_overwrite = False
+        self.base_commit = None
+        self.branch = None
 
         # Written in MakeCcFile()
         #  key: name of patch file

tools/u_boot_pylib/gitutil.py

@@ -701,13 +701,38 @@ def setup():
                        .return_code == 0)
 
 
+def get_hash(spec):
+    """Get the hash of a commit
+
+    Args:
+        spec (str): Git commit to show, e.g. 'my-branch~12'
+
+    Returns:
+        str: Hash of commit
+    """
+    return command.output_one_line('git', 'show', '-s', '--pretty=format:%H',
+                                   spec)
+
+
 def get_head():
     """Get the hash of the current HEAD
 
     Returns:
         Hash of HEAD
     """
-    return command.output_one_line('git', 'show', '-s', '--pretty=format:%H')
+    return get_hash('HEAD')
+
+
+def get_branch():
+    """Get the branch we are currently on
+
+    Return:
+        str: branch name, or None if none
+    """
+    out = command.output_one_line('git', 'rev-parse', '--abbrev-ref', 'HEAD')
+    if out == 'HEAD':
+        return None
+    return out
 
 
 if __name__ == "__main__":