[PATCH v2 4/4] subtree: improve decision on merges kept in split
- From
Roger Strain <rstrain@swri.org>
- Date
- Oct 11, 2018, 19:46 UTC
- Message-ID
- <20181011194605.19518-5-rstrain@swri.org>
- In-Reply-To
- <20180928183540.48968-1-roger.strain@swri.org>
From: "Strain, Roger L" <roger.strain@swri.org>
When multiple identical parents are detected for a commit being considered for copying, explicitly check whether one is the common merge base between the commits. If so, the other commit can be used as the identical parent; if not, a merge must be performed to maintain history.
In some situations two parents of a merge commit may appear to both have identical subtree content with each other and the current commit. However, those parents can potentially come from different commit graphs.
Previous behavior would simply select one of the identical parents to serve as the replacement for this commit, based on the order in which they were processed.
New behavior compares the merge base between the commits to determine if a new merge commit is necessary to maintain history despite the identical content.
Signed-off-by: Strain, Roger L <roger.strain@swri.org> --- contrib/subtree/git-subtree.sh | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh index eef4199ae..7dd643998 100755 --- a/contrib/subtree/git-subtree.sh +++ b/contrib/subtree/git-subtree.sh @@ -541,6 +541,7 @@ copy_or_skip () { nonidentical= p= gotparents= + copycommit= for parent in $newparents do ptree=$(toptree_for_commit $parent) || exit $? @@ -548,7 +549,24 @@ copy_or_skip () { if test "$ptree" = "$tree" then # an identical parent could be used in place of this rev. - identical="$parent" + if test -n "$identical" + then + # if a previous identical parent was found, check whether + # one is already an ancestor of the other + mergebase=$(git merge-base $identical $parent) + if test "$identical" = "$mergebase" + then + # current identical commit is an ancestor of parent + identical="$parent" + elif test "$parent" != "$mergebase" + then + # no common history; commit must be copied + copycommit=1 + fi + else + # first identical parent detected + identical="$parent" + fi else nonidentical="$parent" fi @@ -571,7 +589,6 @@ copy_or_skip () { fi done - copycommit= if test -n "$identical" && test -n "$nonidentical" then extras=$(git rev-list --count $identical..$nonidentical)
-- 2.19.1