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
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")"
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.
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.