patman: Allow specifying the message ID your series is in reply to

Some versions of git don't seem to prompt you for the message ID that
your series is in reply to.  Allow specifying this from the command
line.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/gitutil.py b/tools/patman/gitutil.py
index 99fac79..4e21d4c 100644
--- a/tools/patman/gitutil.py
+++ b/tools/patman/gitutil.py
@@ -317,7 +317,7 @@
     return result
 
 def EmailPatches(series, cover_fname, args, dry_run, cc_fname,
-        self_only=False, alias=None):
+        self_only=False, alias=None, in_reply_to=None):
     """Email a patch series.
 
     Args:
@@ -327,6 +327,8 @@
         dry_run: Just return the command that would be run
         cc_fname: Filename of Cc file for per-commit Cc
         self_only: True to just email to yourself as a test
+        in_reply_to: If set we'll pass this to git as --in-reply-to.
+            Should be a message ID that this is in reply to.
 
     Returns:
         Git command that was/would be run
@@ -376,6 +378,9 @@
         to = BuildEmailList([os.getenv('USER')], '--to', alias)
         cc = []
     cmd = ['git', 'send-email', '--annotate']
+    if in_reply_to:
+        cmd.append('--in-reply-to="%s"' % in_reply_to)
+
     cmd += to
     cmd += cc
     cmd += ['--cc-cmd', '"%s --cc-cmd %s"' % (sys.argv[0], cc_fname)]