Rebasing local git branches on the new repo

[Jonathan Wakely]

Now that I've switched my local git tree to the new repo (by changing
the URL for the 'origin' remote, and adding the old one as a 'gcc-old'
remote) I've been experimenting with these commands to switch some of
the ~400 local branches to be based on the new repo instead of the
git-svn mirror.

  # The local branch to update
  branch=foo

  # The previous upstream for the branch
  upstream=$(git rev-parse --symbolic-full-name $branch@{u} | sed
-n s,^refs/heads,gcc-old,p)
  # find the last upstream commit in the branch
  base=$(git merge-base $branch $upstream)
  # extract its SVN revision
  svnrev=$(git log -1 $base | sed -n
'/git-svn-id:/s/.*@\([[:digit:]]\+\) .*/\1/p')
  # find equivalent commit in master
  onto=$(git log --pretty=format:%H --grep="From-SVN: r$svnrev" $branch@{u})

  git rebase --onto $onto $upstream $branch

Use at your own risk!

Re: GIT: Monotonically increasing trunk and release branch ids

[Jakub Jelinek]

On Sat, Jan 11, 2020 at 11:03:02AM +0100, Jakub Jelinek wrote:
> Here it is in patch form (against Joseph's git-hooks copy), but untested
> (both because the repo isn't converted yet, basepoints don't exist there
> either and because not sure how exactly it can be tested in a dry-run, say
> sending me mail instead of to the public list etc.).
> So, all I did test is some simple thing in python3 interactively because
> it is close to 20 years since I used python regularly.

This is what I've actually committed after testing it (in
gcc-reposurgeon-8.git) and Joseph's approval.
Example how such mail looks like:
https://gcc.gnu.org/ml/gcc-cvs/2020-01/msg00396.html
and https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93218#c3 for bugzilla
comment.  Commits to branches other than master or releases/gcc-* are
unaffected.
If we get the https://gcc.gnu.org/g: redirector working, we should change
the URLs emitted in both gcc-cvs mails and in bugzilla, because at least in
bugzilla the 87 chars long URL is too long and wraps around.

diff --git a/hooks/updates/__init__.py b/hooks/updates/__init__.py
index c5d8181..9d9e1dc 100644
--- a/hooks/updates/__init__.py
+++ b/hooks/updates/__init__.py
@@ -299,6 +299,19 @@ class AbstractUpdate(object):
 # name in full to label the branch name.
 branch = '(%s)' % self.ref_name
 
+# GCC monotonically increasing commit ids.
+rev_id = ''
+if (self.email_info.project_name.startswith('gcc')
+and (self.short_ref_name == 'master'
+ or self.short_ref_name.startswith('releases/gcc-'))):
+rev_id = git.describe(commit.rev, all=True, abbrev='40',
+  match='basepoints/gcc-[0-9]*')
+if rev_id.startswith('basepoints/gcc-'):
+rev_id = 'r' + rev_id[len('basepoints/gcc-'):]
+branch = ' ' + rev_id[:rev_id.find('-g')]
+else:
+rev_id = ''
+
 subject = '[%(repo)s%(branch)s] %(subject)s' % {
 'repo': self.email_info.project_name,
 'branch': branch,
@@ -322,6 +335,10 @@ class AbstractUpdate(object):
 # by stripping it from the output.
 
 body = git.log(commit.rev, max_count="1") + '\n'
+
+if rev_id:
+body = re.sub(r'^commit ' + commit.rev, 'commit ' + rev_id,
+  body, 1, re.M)
 if git_config('hooks.commit-url') is not None:
 url_info = {'rev': commit.rev,
 'ref_name': self.ref_name}


Jakub