patman: Use the Change-Id, version, and prefix in the Message-Id

As per the centithread on ksummit-discuss [1], there are folks who
feel that if a Change-Id is present in a developer's local commit that
said Change-Id could be interesting to include in upstream posts.
Specifically if two commits are posted with the same Change-Id there's
a reasonable chance that they are either the same commit or a newer
version of the same commit.  Specifically this is because that's how
gerrit has trained people to work.

There is much angst about Change-Id in upstream Linux, but one thing
that seems safe and non-controversial is to include the Change-Id as
part of the string of crud that makes up a Message-Id.

Let's give that a try.

In theory (if there is enough adoption) this could help a tool more
reliably find various versions of a commit.  This actually might work
pretty well for U-Boot where (I believe) quite a number of developers
use patman, so there could be critical mass (assuming that enough of
these people also use a git hook that adds Change-Id to their
commits).  I was able to find this git hook by searching for "gerrit
change id git hook" in my favorite search engine.

In theory one could imagine something like this could be integrated
into other tools, possibly even git-send-email.  Getting it into
patman seems like a sane first step, though.

NOTE: this patch is being posted using a patman containing this patch,
so you should be able to see the Message-Id of this patch and see that
it contains my local Change-Id, which ends in 2b9 if you want to
check.

[1] https://lists.linuxfoundation.org/pipermail/ksummit-discuss/2019-August/006739.html

Signed-off-by: Douglas Anderson <dianders@chromium.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/patman/commit.py b/tools/patman/commit.py
index 2bf3a0b..48d0529 100644
--- a/tools/patman/commit.py
+++ b/tools/patman/commit.py
@@ -21,6 +21,8 @@ class Commit:
             The dict is indexed by change version (an integer)
         cc_list: List of people to aliases/emails to cc on this commit
         notes: List of lines in the commit (not series) notes
+        change_id: the Change-Id: tag that was stripped from this commit
+            and can be used to generate the Message-Id.
     """
     def __init__(self, hash):
         self.hash = hash
@@ -30,6 +32,7 @@ class Commit:
         self.cc_list = []
         self.signoff_set = set()
         self.notes = []
+        self.change_id = None
 
     def AddChange(self, version, info):
         """Add a new change line to the change list for a version.