patman: Allow reading metadata from a list of commits

We normally read from the current branch, but buildman will need to look
at commits from another branch. Allow the metadata to be read from any
list of commits, to provide this flexibility.

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

tools/patman/patchstream.py

@@ -237,7 +237,8 @@ class PatchStream:
         # Detect the start of a new commit
         elif commit_match:
             self.CloseCommit()
-            self.commit = commit.Commit(commit_match.group(1)[:7])
+            # TODO: We should store the whole hash, and just display a subset
+            self.commit = commit.Commit(commit_match.group(1)[:8])
 
         # Detect tags in the commit message
         elif tag_match:
@@ -334,6 +335,35 @@ class PatchStream:
         self.Finalize()
 
 
+def GetMetaDataForList(commit_range, git_dir=None, count=None,
+                       series = Series()):
+    """Reads out patch series metadata from the commits
+
+    This does a 'git log' on the relevant commits and pulls out the tags we
+    are interested in.
+
+    Args:
+        commit_range: Range of commits to count (e.g. 'HEAD..base')
+        git_dir: Path to git repositiory (None to use default)
+        count: Number of commits to list, or None for no limit
+        series: Series object to add information into. By default a new series
+            is started.
+    Returns:
+        A Series object containing information about the commits.
+    """
+    params = ['git', 'log', '--no-color', '--reverse', commit_range]
+    if count is not None:
+        params[2:2] = ['-n%d' % count]
+    if git_dir:
+        params[1:1] = ['--git-dir', git_dir]
+    pipe = [params]
+    stdout = command.RunPipe(pipe, capture=True).stdout
+    ps = PatchStream(series, is_log=True)
+    for line in stdout.splitlines():
+        ps.ProcessLine(line)
+    ps.Finalize()
+    return series
+
 def GetMetaData(start, count):
     """Reads out patch series metadata from the commits
 
@@ -344,15 +374,7 @@ def GetMetaData(start, count):
         start: Commit to start from: 0=HEAD, 1=next one, etc.
         count: Number of commits to list
     """
-    pipe = [['git', 'log', '--no-color', '--reverse', 'HEAD~%d' % start,
-	'-n%d' % count]]
-    stdout = command.RunPipe(pipe, capture=True).stdout
-    series = Series()
-    ps = PatchStream(series, is_log=True)
-    for line in stdout.splitlines():
-        ps.ProcessLine(line)
-    ps.Finalize()
-    return series
+    return GetMetaDataForList('HEAD~%d' % start, None, count)
 
 def FixPatch(backup_dir, fname, series, commit):
     """Fix up a patch file, by adding/removing as required.