diff options
| author |  Joey Hess <joey@kitenet.net> | 2011-11-06 15:18:45 -0400 |
|---|---|---|
| committer | Joey Hess <joey@kitenet.net> | 2011-11-06 15:22:40 -0400 |
| commit | c99fb589097d96b4e10cd8b137f72881cdb93118 (patch) | |
| tree | bf26fa39ad83a2df6558e76466137e6d209c2395 /debian | |
| parent | bf07e2c921f66965ca0be816975fc608a81c4276 (diff) | |
merge: Use fast-forward merges when possible.
Thanks Valentin Haenel for a test case showing how non-fast-forward merges
could result in an ongoing pull/merge/push cycle.
While the git-annex branch is fast-forwarded, git-annex's index file is still
updated using the union merge strategy as before. There's no other way to
update the index that would be any faster.
It is possible that a union merge and a fast-forward result in different file
contents: Files should have the same lines, but a union merge may change
their order. If this happens, the next commit made to the git-annex branch
will have some unnecessary changes to line orders, but the consistency
of data should be preserved.
Note that when the journal contains changes, a fast-forward is never attempted,
which is fine, because committing those changes would be vanishingly unlikely
to leave the git-annex branch at a commit that already exists in one of
the remotes.
The real difficulty is handling the case where multiple remotes have all
changed. git-annex does find the best (ie, newest) one and fast forwards
to it. If the remotes are diverged, no fast-forward is done at all. It would
be possible to pick one, fast forward to it, and make a merge commit to
the rest, I see no benefit to adding that complexity.
Determining the best of N changed remotes requires N*2+1 calls to git-log, but
these are fast git-log calls, and N is typically small. Also, typically
some or all of the remote refs will be the same, and git-log is not called to
compare those. In the real world I expect this will almost always add only
1 git-log call to the merge process. (Which already makes N anyway.)
Diffstat (limited to 'debian')
| -rw-r--r-- | debian/changelog | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/debian/changelog b/debian/changelog index fdd3cb7f6..57be53c85 100644 --- a/debian/changelog +++ b/debian/changelog @@ -1,3 +1,11 @@ +git-annex (3.20111106) UNRELEASED; urgency=low + + * merge: Use fast-forward merges when possible. + Thanks Valentin Haenel for a test case showing how non-fast-forward + merges could result in an ongoing pull/merge/push cycle. + + -- Joey Hess <joeyh@debian.org> Sun, 06 Nov 2011 14:57:57 -0400 + git-annex (3.20111105) unstable; urgency=low * The default backend used when adding files to the annex is changed |