From mboxrd@z Thu Jan  1 00:00:00 1970
From: Luben Tuikov <ltuikov@yahoo.com>
Subject: Question on empty commit
Date: Fri, 13 Jan 2006 18:18:00 -0800 (PST)
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Hi,

Scenario:

trunk remote
  |
  \/
trunk local
     \
      `--> tree A
               \
                `--> tree B

         Figure 1.

This is the dependecny since project B depends on project A
introduced in tree A.  And merging is done as follows
(branch per directory; everything but HEAD and index is shared):

cd trunk && git pull trunk
cd ../treeA && git merge "merge trunk" HEAD trunk
cd ../treeB && git merge "merge tree A" HEAD treeA

But this isn't the only way to do it since tree B depends
only on the introduced into tree A project A, and both
project A and project B depend on the trunk, as follows:

trunk remote
  |
  \/
trunk local
  \  \
   \  `--> tree A
    \          \
     `--------> `--> tree B

         Figure 2.

So at point in time t where tree B had been synced with tree A,
and tree A had been synced with trunk, but trunk had _not_ been
synced with remote trunk, a merge was done following Figure 2:

cd trunk && git pull trunk
cd ../treeA && git merge "merge trunk" HEAD trunk
cd ../treeB && git merge "merge trunk" HEAD trunk
git merge "merge tree A" HEAD treeA

Now the last merge introduced an empty commit, since
tree A and tree B had been in sync (only local and
remote trunk had been out of sync).  While it was expected
that no commit would be introduced since they were in sync.

Was the empty commit correct behavior?

Thanks,
   Luben