threads / discuss / 10038

git-svn and branches

Subject: git-svn and branches

## tl;dr

4 messages between Sep 27, 2007 and Sep 28, 2007.

replies: 3people: 3as markdown or json

Steven Walter· Sep 27, 2007, 02:12 UTC · lore

I'm using git-svn to track a rather large subversion repository with a non-standard layout. In the past, I've only cared about trunk, but now I need to occasionally use branches, too. By adding a second git-svn remote with the branch URL, I can fetch the branch, and git-svn is even intelligent enough to notice that the branch was copied off of trunk.

However, git-svn also does a complete checkout for the first revision of the branch. By this, I mean it goes through shows "A file" for every file in the repository. This takes quite a while, and seems rather unnecessary given that git-svn already noticed that the branch shares a history with trunk, which is already fetched.

Knowing just enough of what git-svn is doing to be dangerous, I whipped up a short little patch. This patch seems to work for the common case, and avoids fetching every file from subversion. It does break sometimes, however, and I don't understand why.

Maybe someone with a better grasps of the code can see what I did wrong, or suggest a better means to my end?

diff --git a/git-svn.perl b/git-svn.perl
index 484b057..1bc92b6 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -1848,9 +1848,10 @@ sub find_parent_branch {
                                              $self->full_url, $ed)
                          or die "SVN connection failed somewhere...\n";
                } else {
+                       $self->assert_index_clean($parent);
                        print STDERR "Following parent with do_update\n";
                        $ed = SVN::Git::Fetcher->new($self);
-                       $self->ra->gs_do_update($rev, $rev, $self, $ed)
+                       $self->ra->gs_do_update($rev, $r0, $self, $ed)
                          or die "SVN connection failed somewhere...\n";
                }
                print STDERR "Successfully followed parent\n";

-- 
-Steven Walter <stevenrwalter@gmail.com>
"A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects."
   -Robert Heinlein

Sam Vilain· Sep 27, 2007, 06:36 UTC · re: Steven Walter · lore

Re: git-svn and branches

Steven Walter wrote:

Show 7 quoted lines

> Knowing just enough of what git-svn is doing to be dangerous, I
> whipped up a short little patch.  This patch seems to work for the
> common case, and avoids fetching every file from subversion.  It does
> break sometimes, however, and I don't understand why.
>
> Maybe someone with a better grasps of the code can see what I did
> wrong, or suggest a better means to my end?

Try also with the SVN trunk - the do_switch API has recently been added and it also avoids this excess checkout. I'm not sure why a solution like you post isn't used, perhaps Eric can comment further.

Sam.

Show 16 quoted lines

> diff --git a/git-svn.perl b/git-svn.perl
> index 484b057..1bc92b6 100755
> --- a/git-svn.perl
> +++ b/git-svn.perl
> @@ -1848,9 +1848,10 @@ sub find_parent_branch {
>                                               $self->full_url, $ed)
>                           or die "SVN connection failed somewhere...\n";
>                 } else {
> +                       $self->assert_index_clean($parent);
>                         print STDERR "Following parent with do_update\n";
>                         $ed = SVN::Git::Fetcher->new($self);
> -                       $self->ra->gs_do_update($rev, $rev, $self, $ed)
> +                       $self->ra->gs_do_update($rev, $r0, $self, $ed)
>                           or die "SVN connection failed somewhere...\n";
>                 }
>                 print STDERR "Successfully followed parent\n";

Eric Wong· Sep 27, 2007, 07:24 UTC · re: Steven Walter · lore

Re: git-svn and branches

Steven Walter <stevenrwalter@gmail.com> wrote:

Show 19 quoted lines

> I'm using git-svn to track a rather large subversion repository with a
> non-standard layout.  In the past, I've only cared about trunk, but now
> I need to occasionally use branches, too.  By adding a second git-svn
> remote with the branch URL, I can fetch the branch, and git-svn is even
> intelligent enough to notice that the branch was copied off of trunk.
> 
> However, git-svn also does a complete checkout for the first revision of
> the branch.  By this, I mean it goes through shows "A    file" for every
> file in the repository.  This takes quite a while, and seems rather
> unnecessary given that git-svn already noticed that the branch shares a
> history with trunk, which is already fetched.
> 
> Knowing just enough of what git-svn is doing to be dangerous, I whipped
> up a short little patch.  This patch seems to work for the common case,
> and avoids fetching every file from subversion.  It does break
> sometimes, however, and I don't understand why.
> 
> Maybe someone with a better grasps of the code can see what I did wrong,
> or suggest a better means to my end?

I believe your case handles where a branch is created directly from a trunk copy with no file modifications in the branch, but not when a branch is created and files are modified in the trunk (or branch) within the same revision. Is this what's happening?

Additionally, I think this breaks when an entire trunk or branch is moved around because the original directory has moved or gone away:

  /trunk => /project-a/trunk

Anyways, as Sam said, newer SVN (1.4.4+) has a working do_switch() function and that code path will never be hit at all.

Show 16 quoted lines

> diff --git a/git-svn.perl b/git-svn.perl
> index 484b057..1bc92b6 100755
> --- a/git-svn.perl
> +++ b/git-svn.perl
> @@ -1848,9 +1848,10 @@ sub find_parent_branch {
>                                               $self->full_url, $ed)
>                           or die "SVN connection failed somewhere...\n";
>                 } else {
> +                       $self->assert_index_clean($parent);
>                         print STDERR "Following parent with do_update\n";
>                         $ed = SVN::Git::Fetcher->new($self);
> -                       $self->ra->gs_do_update($rev, $rev, $self, $ed)
> +                       $self->ra->gs_do_update($rev, $r0, $self, $ed)
>                           or die "SVN connection failed somewhere...\n";
>                 }
>                 print STDERR "Successfully followed parent\n";

-- 
Eric Wong

Steven Walter· Sep 28, 2007, 17:19 UTC · re: Eric Wong · lore

Re: git-svn and branches

On Thu, Sep 27, 2007 at 12:24:04AM -0700, Eric Wong wrote:

Show 12 quoted lines

> I believe your case handles where a branch is created directly from a
> trunk copy with no file modifications in the branch, but not when a
> branch is created and files are modified in the trunk (or branch) within
> the same revision.  Is this what's happening?
> 
> Additionally, I think this breaks when an entire trunk or branch is
> moved around because the original directory has moved or gone away:
> 
>   /trunk => /project-a/trunk
> 
> Anyways, as Sam said, newer SVN (1.4.4+) has a working do_switch()
> function and that code path will never be hit at all.

I think you're right that my code would only handle a verbatim copy. I made a few changes and I think I have something that is more generally useful. Using a newer version of subversion isn't practical for me, as this is a work situation where I don't have control of the workstations.

One criticism of the patch: the trees_match function probably needs to be re-written. My SVN::Perl-foo is weak.

Patch to follow

-- 
-Steven Walter <stevenrwalter@gmail.com>
"A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects."
   -Robert Heinlein