[PATCH] git-rebase--interactive.sh: preserve-merges fails on merges created with no-ff

'git rebase' uses 'git merge' to preserve merges (-p). This preserves the original merge commit correctly, except when the original merge commit was created by 'git merge --no-ff'. In this case, 'git rebase' will fail to preserve the merge, because during 'git rebase', 'git merge' will simply fast-forward and skip the commit. For example:

               B
              / \
             A---M
            /
    ---o---O---P---Q

If we try to rebase M onto P, we lose the merge commit and this happens:

                 A---B
                /
    ---o---O---P---Q

To correct this, we simply do a "no fast-forward" on all merge commits when rebasing. Since by the time we decided to do a 'git merge' inside 'git rebase', it means there was a merge originally, so 'git merge' should always create a merge commit regardless of what the merge branches look like. This way, when rebase M onto P from the above example, we get:

                   B
                  / \
                 A---M
                /
    ---o---O---P---Q

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 git-rebase--interactive.sh |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)