In order to push changes to our master branch, one has to have pulled
first. We pull with the --rebase option. It works great except for
merge commits.
I discovered 'git rebase' has a --preserve-merges option. I assumed it
would allow me to rebase my merge commit on top of others' changes
pushed to our central master branch.
Unfortunately, I can't seem to make it work. Does anyone have thoughts
on what I'm doing wrong?
My session is below.
Thanks!
Josh
$ git init
$ echo a > a
$ git add a
$ git commit -m a
$ git tag a
$ echo b > b
$ git add b
$ git commit -m b
$ echo c > c
$ git add c
$ git commit -m c
$ git tag c
# Note the hierarchy is simple: a <- b <- c
$ git lg --all
* d132c87 - (c) c
* 4a88fd1 - b
* b576660 - (a) a
# Create the hierarchy: a <- d
$ git checkout a
Note: checking out 'a'.
$ echo d > d
$ git add d
$ git commit -m d
$ git tag d
$ git lg --all
* 6abf527 - (HEAD, d) d
| * d132c87 - (c) c
| * 4a88fd1 - b
|/
* b576660 - (a) a
# Wanting to merge my branch back to my local master to push to the server.
$ git checkout a
$ git merge --no-ff c
Merge made by recursive.
b | 1 +
c | 1 +
2 files changed, 2 insertions(+), 0 deletions(-)
create mode 100644 b
create mode 100644 c
$ git tag bc-merge
# Commit 'd' is something I would pull --rebase from the server before I
push.
$ git lg --all
* 472fd93 - (HEAD, bc-merge) Merge commit 'c' into HEAD (3 seconds ago)
|\
| * d132c87 - (c) c (2 minutes ago)
| * 4a88fd1 - b (2 minutes ago)
|/
| * 6abf527 - (d) d (2 minutes ago)
|/
* b576660 - (a, master) a (3 minutes ago)
# Here is the rebase with the --preserve-merges option.
$ git rebase --preserve-merges d
Rebasing (n/3)
Successfully rebased and updated detached HEAD.
# Of course, bc-merge is an orphaned branch. Its changes got replayed
on top of 'd'.
# Note the merge commit with the description "Merge commit 'c' into
HEAD" is missing.
$ git lg --all
* 2c93a8a - (HEAD) c (11 seconds ago)
* 2b98bc6 - b (11 seconds ago)
* 6abf527 - (d) d (3 minutes ago)
| * 472fd93 - (bc-merge) Merge commit 'c' into HEAD (74 seconds ago)
| |\
|/ /
| * d132c87 - (c) c (3 minutes ago)
| * 4a88fd1 - b (3 minutes ago)
|/
* b576660 - (a, master) a (4 minutes ago)
On 2010.09.08 23:17:39 -0600, Joshua Jensen wrote:
# Commit 'd' is something I would pull --rebase from the server
before I push.
$ git lg --all
* 472fd93 - (HEAD, bc-merge) Merge commit 'c' into HEAD (3 seconds ago)
|\
| * d132c87 - (c) c (2 minutes ago)
| * 4a88fd1 - b (2 minutes ago)
|/
| * 6abf527 - (d) d (2 minutes ago)
|/
* b576660 - (a, master) a (3 minutes ago)
# Here is the rebase with the --preserve-merges option.
$ git rebase --preserve-merges d
Rebasing (n/3)
Successfully rebased and updated detached HEAD.
# Of course, bc-merge is an orphaned branch. Its changes got
replayed on top of 'd'.
Yup, and the "problem" is, that both sides of the merge got replayed.
# Note the merge commit with the description "Merge commit 'c' into
HEAD" is missing.
Because the merge could be resolved as a fast-forward, as it merges the
replayed commits b' and c', not the originals.
$ git lg --all
* 2c93a8a - (HEAD) c (11 seconds ago)
* 2b98bc6 - b (11 seconds ago)
* 6abf527 - (d) d (3 minutes ago)
| * 472fd93 - (bc-merge) Merge commit 'c' into HEAD (74 seconds ago)
| |\
|/ /
| * d132c87 - (c) c (3 minutes ago)
| * 4a88fd1 - b (3 minutes ago)
|/
* b576660 - (a, master) a (4 minutes ago)
What you actually wanted to replay is just the first-parent history,
redoing the merges with their respective original second parent.
Jonathan (Cc'ed) had the same problem about a month ago.
The "first parent" thing isn't that well defined, criss-cross merges
combined with some unfortunate fast-forwards will easily make the
first-parent history become the one that you didn't mean (ask any
git-svn users that dared to use "git merge" without fully understanding
how git-svn uses the history ;-)), but it works in this special case.
And with that special case in mind (and admittedly probably not thinking
much further) I came up with this patch a few years ago:
http://marc.info/?l=git&m=119379735525213&w=2
It was not my itch to scratch though, so I never got around to get it
included, and of course it doesn't apply cleanly anymore. I tried to
give some hints to Jonathan ("hachi") on #git on how to update the patch
to make it apply again:
http://colabti.de/irclogger/irclogger_log/git?date=2010-08-20#l1241
Feel free to pick up from there...
Björn
----- Original Message -----
From: Björn Steinbrink
Date: 9/8/2010 11:51 PM
quoted
$ git lg --all
* 2c93a8a - (HEAD) c (11 seconds ago)
* 2b98bc6 - b (11 seconds ago)
* 6abf527 - (d) d (3 minutes ago)
| * 472fd93 - (bc-merge) Merge commit 'c' into HEAD (74 seconds ago)
| |\
|/ /
| * d132c87 - (c) c (3 minutes ago)
| * 4a88fd1 - b (3 minutes ago)
|/
* b576660 - (a, master) a (4 minutes ago)
What you actually wanted to replay is just the first-parent history,
redoing the merges with their respective original second parent.
Jonathan (Cc'ed) had the same problem about a month ago.
The "first parent" thing isn't that well defined, criss-cross merges
combined with some unfortunate fast-forwards will easily make the
first-parent history become the one that you didn't mean (ask any
git-svn users that dared to use "git merge" without fully understanding
how git-svn uses the history ;-)), but it works in this special case.
And with that special case in mind (and admittedly probably not thinking
much further) I came up with this patch a few years ago:
http://marc.info/?l=git&m=119379735525213&w=2
I hand merged your change in to my Git installation. There is one part
of git-rebase--interactive that looks entirely different, so I would
need to look back through the history to determine how to properly apply it.
The good news is the patch does exactly what I want in this simple
case. I will have to try it on some more complicated hierarchies to see
what the end result is.
It's curious... whenever I ask around about issue X or feature Y, a
previously submitted patch can generally be found in the list archives. :)
Josh