Syncing with CVS

Syncing with CVS

[Christian von Kietzell]

Hi,

I have a project I started in git. After a while I exported that to
CVS via git cvsexportcommit which worked quite nicely. Now, a
colleague made changes to the project - in CVS. What's the best way to
get those back into my git repository so that I'll be able to sync
back and forth between git and CVS? I had a quick look at the wiki but
couldn't find anything appropriate.

I know of git cvsimport, of course, but that doesn't work on my
original repository. Or does it? I didn't find anything on how to
limit what to import. After all, some of the commits are already in my
repository (the ones I exported).

Hope any of you can help. Thanks in advance.

  Chris

Re: Syncing with CVS

[Johan Herland]

On Monday 19 January 2009, Christian von Kietzell wrote:
> Hi,
>
> I have a project I started in git. After a while I exported that to
> CVS via git cvsexportcommit which worked quite nicely. Now, a
> colleague made changes to the project - in CVS. What's the best way
> to get those back into my git repository so that I'll be able to sync
> back and forth between git and CVS? I had a quick look at the wiki
> but couldn't find anything appropriate.
>
> I know of git cvsimport, of course, but that doesn't work on my
> original repository. Or does it? I didn't find anything on how to
> limit what to import. After all, some of the commits are already in
> my repository (the ones I exported).
>
> Hope any of you can help. Thanks in advance.

Unfortunately bidirectional syncing between CVS and Git is pretty much 
impossible in the general case, because CVS's structure is so different 
from Git's. For one, it is very easy to (re)move tags and branches in 
CVS, with no record of where it was moved from. (Also, as anybody 
involved in proper CVS-to-Git converters ("git cvsimport" does _not_ 
fall into this category) will tell you, recreating history from CVS is 
a highly non-trivial task in itself.) This means that even if you have 
imported some CVS state into Git, you cannot guarantee that the CVS 
state has not changed the next time you try to import. Therefore, it is 
very hard to determine whether you're importing a whole new branch from 
CVS, or whether you are just incrementally importing patches on top of 
a previously imported branch.

I have a similar situation at $dayjob, where we have a central CVS 
server with the official version, and I use Git for working locally. In 
this case, I use "git cvsexportcommit" to propagate my local changes to 
the CVS server. I only use this approach on branches where nobody else 
is allowed to commit (of course CVS does not enforce this rule, so I 
have to manually make sure that does not happen). If someone else were 
to commit to my branch in CVS, I would have to redo a full CVS-to-Git 
conversion, in order to get a new Git repo that is in sync with CVS. I 
can then resume "git cvsexportcommit" to propagate my changes from Git 
to CVS.


Have fun! :)

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net

Re: Syncing with CVS

[Boaz Harrosh]

Christian von Kietzell wrote:
> Hi,
> 
> I have a project I started in git. After a while I exported that to
> CVS via git cvsexportcommit which worked quite nicely. Now, a
> colleague made changes to the project - in CVS. What's the best way to
> get those back into my git repository so that I'll be able to sync
> back and forth between git and CVS? I had a quick look at the wiki but
> couldn't find anything appropriate.
> 
> I know of git cvsimport, of course, but that doesn't work on my
> original repository. Or does it? I didn't find anything on how to
> limit what to import. After all, some of the commits are already in my
> repository (the ones I exported).
> 
> Hope any of you can help. Thanks in advance.
> 
>   Chris

I would "git cvsimport" into temporary new git.
Then "git remote add cvs_import that_temp_git" into the main git
Then find the point of the common base, do
"git tag CVS_GIT_BASE that_base_commit_uid"
"git checkout -b cvs_import cvs_import/master"
"git rebase --onto master CVS_GIT_BASE"

So in fact I'm just cherry-picking the additions from CVS
and reapplying on to original git tree. If you want it more
automatic you'll need to do the above in a script with some
kind of naming conventions for your git tags and CVS's tags
at points of sync.

Boaz
 

Re: Syncing with CVS

[Robin Rosenberg]

måndag 19 januari 2009 10:39:53 skrev Christian von Kietzell:
> Hi,
> 
> I have a project I started in git. After a while I exported that to
> CVS via git cvsexportcommit which worked quite nicely. Now, a
> colleague made changes to the project - in CVS. What's the best way to
> get those back into my git repository so that I'll be able to sync
> back and forth between git and CVS? I had a quick look at the wiki but
> couldn't find anything appropriate.
> 
> I know of git cvsimport, of course, but that doesn't work on my
> original repository. Or does it? I didn't find anything on how to
> limit what to import. After all, some of the commits are already in my
> repository (the ones I exported).
Just continue with cvsimport, then git rebase origin. That'll drop the
commits that you made when the same commit have been discovered
in CVS.

I personally do the cvs import into a separate repo using a cron job. That
extra repo is my origin so I get up-to-date using git fetch and rebase just
as if the CVS commits would come from a real repo.

-- robin