Rebasing Git for Windows

To do a rebase of the Git for Windows source onto a new upstream Git release, follow this guideline.

Assumptions

1. You want to rebase onto a new upstream release tagged as v2.3.4
2. The latest rebase was done onto a upstream release tagged as v2.3.3

Preconditions

1. A working Git for Windows SDK.
2. A fetched build-extra repository.
   cd /usr/src/build-extra
git fetch
git checkout master (git pull if your branch is behind the upstream)
3. Working directory set to current Git for Windows source.
   cd /usr/src/git
4. Added upstream as a remote.
   git remote add git https://github.com/git/git
git fetch git

Starting the rebase

1. Find the commit of the last rebase and remember it.
   BASE="$(git rev-parse ":/Start the merging-rebase")" or possibly
   BASE="$(git rev-parse HEAD^{"/Start the merging-rebase}")" if there have been
   trial merging rebases on other branches. Check with
   git log -1 $BASE and git branch -a --contains $BASE.
2. Run the shears.sh script to build up the actual rebase script.
   ../build-extra/./shears.sh --merging --onto v2.3.4 $BASE
   Note: v2.3.4 is a tag in the remote git.
   See the script if you are testing changes initiated in a local branch of the git upstream.
3. The rebase should start automatically and occasionally stop if it hits any merge conflicts. Resolve those conflicts and then continue the rebase.
   git rebase --continue

Verifying the rebase

1. Generate a diff of the previous state.
   git diff v2.3.3..origin/master > prev.diff

2. Generate a diff of the current state.
   git diff v2.3.4..master > curr.diff

3. Diff the diffs.
   git diff --no-index prev.diff curr.diff

   Ideally, the resulting output will show changes only in the @@ lines of prev.diff vs curr.diff.
   It's a bit hard to read, though, because it is a diff of a diff.
   So meta.
   When there is a line that starts with a - or a + but then continues with a space, that's good!
   It means that the context of our changes changed.

The newer git range-diff may also be used.