What does "Do not merge" mean in some of the Android git commits?

[Mac Wang]

Hi,

I'm curious about it for long time. I saw a lot of Android git commits were labeled as "Do not merge". But they are merged in to some other branch. (ex. ics-mr1).

So what does it really mean in Google internally?

Mac

[Jean-Baptiste Queru]

We (Google) routinely develop on multiple branches at the same time.
In order to make sure that the later branch (e.g. ics-mr1) contains
all the new features and bugfixes developed in an older branch (e.g.
ics-mr0), we have a server that automatically takes every commit made
in ics-mr0 and merges it into ics-mr1.

However, sometimes the engineer making a change in ics-mr0 knows that
this change doesn't apply to ics-mr1, e.g. because a similar issue was
fixed differently in ics-mr1 and the fix from ics-mr0 wasn't
necessary. In that case, the engineer includes the words "do not
merge" in their change description, and the auto-merger performs a
"git merge -s ours" instead of "git merge" when handling that change.

There's a bit more complexity involved, but that's the high-level view.

JBQ

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Jean-Baptiste M. "JBQ" Queru
Software Engineer, Android Open-Source Project, Google.

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