Welcome to Rebase Hell!

2009-02-28 Thread Daniel Spiewak
Those of you following development progress using Git are probably starting
to notice that the classical Vic Master is no longer the all-knowing
source of data.  Actually, Assaf's GitHub fork has become the more
trustworthy one.  This is because upon its exit from incubation, Buildr gets
to move its SVN repository to a new URL.  This is good for the project, but
bad for the Git forks since git-svn stores the URL information in its commit
messages.

The solution of course is to re-clone from SVN, which I assume exactly what
Assaf did.  There result is a repository which contains all of the same SVN
commits as Vic's, but different messages and very different SHA1 revisions,
meaning that Git has a much harder time merging between the two.  I
discovered this when I attempted to merge Assaf's latest changes with my
master (forked from Vic's).  57 conflicts later (all petty, little issues
unrelated to my additions), I finally had a working master with the latest
commits.  Unfortunately, when I cloned Assaf's repository directly and
attempted to merge back some of my changes, it became very apparent that I
would need to fix the issue in a more scientific manner.

Long story short, the solution is to rebase all of your branches onto
Assaf's master.  I did this by finding the exact commit where I diverged
from vic (I had it tagged, actually) as well as the corresponding commit in
Assaf's master.  These commits I tagged branch-point and
new-branch-point, respectively.  Then for each branch, I did something
like the following:

git checkout scala-joint-compilation
git rebase new-branch-point

Once this was done, I went back to my master and performed a similar
procedure:

git checkout master
git rebase -s ours new-branch-point

This effectively wiped out all of my changes in that branch (it's possible
that some commits may remain if you try it, but none did in my case).  Once
this was done, I went and picked through my origin/master log to see what I
was missing.  This meant re-merging all of my branches:

git merge scala-joint-compilation
git merge clojure
...

Also, I had to cherry-pick a few commits that I had done on master (like
four or five):

git cherry-pick all-your-ant-base
...

Once this was done, I pushed the result back to GitHub:

git push -f origin

The one caveat to this approach is I had all of my changes on numerous
separate branches (for patching reasons).  All of these branches were
branched off of the same point on vic/master.  Since there hadn't been any
merging *between* the branches (only onto master), it was fairly easy to
just rebase these branches onto the new trunk (I only had three conflicts in
the whole process, all easily resolved).  Just judging by GitHub, not many
people are managing their repositories in this fashion.  However, this does
mean that you could be able to just rebase without the -s ours on your
master and come to the same result.

The point is that you will need to perform some conniptions of this sort in
order to fix your repositories, otherwise your changes will remain
incompatible with the Buildr mainline trunk: you won't be able to (easily)
merge assaf/master, and he won't be able to (easily) pull from you.

Incidentally, if anyone has a *better* way of doing this (particularly one
where the entire master history doesn't get wiped out), I'm all ears!  I do
still have the unmerged repository sitting in Time Machine, so I'm perfectly
willing to roll-forward a copy and try again if the result turns out to be
more correct.

Daniel


Re: Welcome to Rebase Hell!

2009-02-28 Thread Assaf Arkin
On Sat, Feb 28, 2009 at 8:52 PM, Daniel Spiewak djspie...@gmail.com wrote:

 Those of you following development progress using Git are probably starting
 to notice that the classical Vic Master is no longer the all-knowing
 source of data.  Actually, Assaf's GitHub fork has become the more
 trustworthy one.  This is because upon its exit from incubation, Buildr
 gets
 to move its SVN repository to a new URL.  This is good for the project, but
 bad for the Git forks since git-svn stores the URL information in its
 commit
 messages.

 The solution of course is to re-clone from SVN, which I assume exactly what
 Assaf did.  There result is a repository which contains all of the same SVN
 commits as Vic's, but different messages and very different SHA1 revisions,
 meaning that Git has a much harder time merging between the two.  I
 discovered this when I attempted to merge Assaf's latest changes with my
 master (forked from Vic's).  57 conflicts later (all petty, little issues
 unrelated to my additions), I finally had a working master with the latest
 commits.  Unfortunately, when I cloned Assaf's repository directly and
 attempted to merge back some of my changes, it became very apparent that I
 would need to fix the issue in a more scientific manner.

 Long story short, the solution is to rebase all of your branches onto
 Assaf's master.  I did this by finding the exact commit where I diverged
 from vic (I had it tagged, actually) as well as the corresponding commit in
 Assaf's master.  These commits I tagged branch-point and
 new-branch-point, respectively.  Then for each branch, I did something
 like the following:

 git checkout scala-joint-compilation
 git rebase new-branch-point

 Once this was done, I went back to my master and performed a similar
 procedure:

 git checkout master
 git rebase -s ours new-branch-point

 This effectively wiped out all of my changes in that branch (it's possible
 that some commits may remain if you try it, but none did in my case).  Once
 this was done, I went and picked through my origin/master log to see what I
 was missing.  This meant re-merging all of my branches:

 git merge scala-joint-compilation
 git merge clojure
 ...

 Also, I had to cherry-pick a few commits that I had done on master (like
 four or five):

 git cherry-pick all-your-ant-base
 ...

 Once this was done, I pushed the result back to GitHub:

 git push -f origin

 The one caveat to this approach is I had all of my changes on numerous
 separate branches (for patching reasons).  All of these branches were
 branched off of the same point on vic/master.  Since there hadn't been any
 merging *between* the branches (only onto master), it was fairly easy to
 just rebase these branches onto the new trunk (I only had three conflicts
 in
 the whole process, all easily resolved).  Just judging by GitHub, not many
 people are managing their repositories in this fashion.  However, this does
 mean that you could be able to just rebase without the -s ours on your
 master and come to the same result.

 The point is that you will need to perform some conniptions of this sort in
 order to fix your repositories, otherwise your changes will remain
 incompatible with the Buildr mainline trunk: you won't be able to (easily)
 merge assaf/master, and he won't be able to (easily) pull from you.

 Incidentally, if anyone has a *better* way of doing this (particularly one
 where the entire master history doesn't get wiped out), I'm all ears!  I do
 still have the unmerged repository sitting in Time Machine, so I'm
 perfectly
 willing to roll-forward a copy and try again if the result turns out to be
 more correct.


Thanks.


AFAIK it's not possible to git svn clone directly from svn.apache.org due to
some weird restriction they placed on the SVN server, it will just keep
git-svn hanging forever. Somehow that doesn't affect incubator projects, or
svn.eu.apache.org, although my starting point was Jukka's unofficial but
somewhat official git mirror[1].


When you git log, check the git-svn-id:

commit a3ab30a66a092bf730950bd95a1394253ebd2f39

Author: Assaf Arkin as...@apache.org

Date:   Fri Feb 27 22:24:50 2009 +


 Fixed RDoc 2.3/2.4 conflict on rake setup.



git-svn-id:
https://svn.eu.apache.org/repos/asf/buildr/tr...@74872213f79535-47bb-0310-9956-ffa450edef68


If two repositories use a different URL -- look for http vs https,
svn.eu.apache.org vs svn.apache.org, asf/buildr vs asf/incubator/buildr --
Git considers them distinct trees (branches). Any time you merge, Git will
have to merge the entire history of these two branches, leading to a lot of
conflicts.

So if you have branches with changes, follow Daniel's instructions. If you
don't, you can still use the -s ours strategy to switch from one branch to
another.

Until Apache comes with a better solution, I'm going to keep my
repository synchronized against  https://svn.eu.apache.org/repos/asf/buildr.
I suggest you all do the same, that way we have the