Teach rebase -i about --preserve-merges
The option "-p" (or long "--preserve-merges") makes it possible to
rebase side branches including merges, without straightening the
history.
Example:
X
\
A---M---B
/
---o---O---P---Q
When the current HEAD is "B", "git rebase -i -p --onto Q O" will yield
X
\
---o---O---P---Q---A'---M'---B'
Note that this will
- _not_ touch X [*1*], it does
- _not_ work without the --interactive flag [*2*], it does
- _not_ guess the type of the merge, but blindly uses recursive or
whatever strategy you provided with "-s <strategy>" for all merges it
has to redo, and it does
- _not_ make use of the original merge commit via git-rerere.
*1*: only commits which reach a merge base between <upstream> and HEAD
are reapplied. The others are kept as-are.
*2*: git-rebase without --interactive is inherently patch based (at
least at the moment), and therefore merges cannot be preserved.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin
Junio C Hamano
parent
68a163c9b4
commit
f09c9b8c5f
@ -9,7 +9,7 @@ SYNOPSIS
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--------
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[verse]
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'git-rebase' [-i | --interactive] [-v | --verbose] [--merge] [-C<n>]
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[--onto <newbase>] <upstream> [<branch>]
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[-p | --preserve-merges] [--onto <newbase>] <upstream> [<branch>]
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'git-rebase' --continue | --skip | --abort
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DESCRIPTION
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@ -213,6 +213,10 @@ OPTIONS
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Make a list of the commits which are about to be rebased. Let the
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user edit that list before rebasing.
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-p, \--preserve-merges::
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Instead of ignoring merges, try to recreate them. This option
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only works in interactive mode.
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include::merge-strategies.txt[]
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NOTES
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@ -304,6 +308,23 @@ $ git rebase -i HEAD~5
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And move the first patch to the end of the list.
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You might want to preserve merges, if you have a history like this:
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------------------
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X
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\
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A---M---B
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/
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---o---O---P---Q
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------------------
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Suppose you want to rebase the side branch starting at "A" to "Q". Make
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sure that the current HEAD is "B", and call
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-----------------------------
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$ git rebase -i -p --onto Q O
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-----------------------------
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Authors
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------
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Written by Junio C Hamano <junkio@cox.net> and
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@ -10,7 +10,8 @@
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# The original idea comes from Eric W. Biederman, in
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# http://article.gmane.org/gmane.comp.version-control.git/22407
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USAGE='(--continue | --abort | --skip | [--onto <branch>] <upstream> [<branch>])'
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USAGE='(--continue | --abort | --skip | [--preserve-merges] [--verbose]
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[--onto <branch>] <upstream> [<branch>])'
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. git-sh-setup
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require_work_tree
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@ -18,6 +19,8 @@ require_work_tree
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DOTEST="$GIT_DIR/.dotest-merge"
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TODO="$DOTEST"/todo
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DONE="$DOTEST"/done
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REWRITTEN="$DOTEST"/rewritten
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PRESERVE_MERGES=
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STRATEGY=
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VERBOSE=
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@ -68,6 +71,8 @@ die_abort () {
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pick_one () {
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case "$1" in -n) sha1=$2 ;; *) sha1=$1 ;; esac
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git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
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test -d "$REWRITTEN" &&
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pick_one_preserving_merges "$@" && return
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parent_sha1=$(git rev-parse --verify $sha1^ 2>/dev/null)
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current_sha1=$(git rev-parse --verify HEAD)
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if [ $current_sha1 = $parent_sha1 ]; then
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@ -79,6 +84,75 @@ pick_one () {
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fi
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}
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pick_one_preserving_merges () {
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case "$1" in -n) sha1=$2 ;; *) sha1=$1 ;; esac
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sha1=$(git rev-parse $sha1)
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if [ -f "$DOTEST"/current-commit ]
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then
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current_commit=$(cat "$DOTEST"/current-commit) &&
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git rev-parse HEAD > "$REWRITTEN"/$current_commit &&
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rm "$DOTEST"/current-commit ||
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die "Cannot write current commit's replacement sha1"
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fi
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# rewrite parents; if none were rewritten, we can fast-forward.
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fast_forward=t
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preserve=t
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new_parents=
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for p in $(git rev-list --parents -1 $sha1 | cut -d\ -f2-)
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do
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if [ -f "$REWRITTEN"/$p ]
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then
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preserve=f
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new_p=$(cat "$REWRITTEN"/$p)
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test $p != $new_p && fast_forward=f
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case "$new_parents" in
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*$new_p*)
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;; # do nothing; that parent is already there
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*)
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new_parents="$new_parents $new_p"
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esac
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fi
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done
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case $fast_forward in
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t)
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echo "Fast forward to $sha1"
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test $preserve=f && echo $sha1 > "$REWRITTEN"/$sha1
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;;
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f)
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test "a$1" = a-n && die "Refusing to squash a merge: $sha1"
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first_parent=$(expr "$new_parents" : " \([^ ]*\)")
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# detach HEAD to current parent
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git checkout $first_parent 2> /dev/null ||
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die "Cannot move HEAD to $first_parent"
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echo $sha1 > "$DOTEST"/current-commit
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case "$new_parents" in
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\ *\ *)
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# redo merge
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author_script=$(get_author_ident_from_commit $sha1)
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eval "$author_script"
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msg="$(git cat-file commit $sha1 | \
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sed -e '1,/^$/d' -e "s/[\"\\]/\\\\&/g")"
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# NEEDSWORK: give rerere a chance
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if ! git merge $STRATEGY -m "$msg" $new_parents
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then
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echo "$msg" > "$GIT_DIR"/MERGE_MSG
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warn Error redoing merge $sha1
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warn
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warn After fixup, please use
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die "$author_script git commit"
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fi
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;;
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*)
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git cherry-pick $STRATEGY "$@" ||
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die_with_patch $sha1 "Could not pick $sha1"
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esac
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esac
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}
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do_next () {
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read command sha1 rest < "$TODO"
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case "$command" in
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@ -155,7 +229,15 @@ do_next () {
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HEADNAME=$(cat "$DOTEST"/head-name) &&
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OLDHEAD=$(cat "$DOTEST"/head) &&
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SHORTONTO=$(git rev-parse --short $(cat "$DOTEST"/onto)) &&
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NEWHEAD=$(git rev-parse HEAD) &&
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if [ -d "$REWRITTEN" ]
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then
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test -f "$DOTEST"/current-commit &&
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current_commit=$(cat "$DOTEST"/current-commit) &&
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git rev-parse HEAD > "$REWRITTEN"/$current_commit
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NEWHEAD=$(cat "$REWRITTEN"/$OLDHEAD)
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else
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NEWHEAD=$(git rev-parse HEAD)
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fi &&
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message="$GIT_REFLOG_ACTION: $HEADNAME onto $SHORTONTO)" &&
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git update-ref -m "$message" $HEADNAME $NEWHEAD $OLDHEAD &&
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git symbolic-ref HEAD $HEADNAME &&
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@ -226,6 +308,9 @@ do
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-v|--verbose)
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VERBOSE=t
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;;
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-p|--preserve-merges)
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PRESERVE_MERGES=t
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;;
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-i|--interactive)
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# yeah, we know
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;;
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@ -274,6 +359,25 @@ do
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echo $UPSTREAM > "$DOTEST"/upstream
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echo $ONTO > "$DOTEST"/onto
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test t = "$VERBOSE" && : > "$DOTEST"/verbose
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if [ t = "$PRESERVE_MERGES" ]
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then
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# $REWRITTEN contains files for each commit that is
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# reachable by at least one merge base of $HEAD and
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# $UPSTREAM. They are not necessarily rewritten, but
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# their children might be.
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# This ensures that commits on merged, but otherwise
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# unrelated side branches are left alone. (Think "X"
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# in the man page's example.)
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mkdir "$REWRITTEN" &&
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for c in $(git merge-base --all $HEAD $UPSTREAM)
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do
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echo $ONTO > "$REWRITTEN"/$c ||
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die "Could not init rewritten commits"
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done
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MERGES_OPTION=
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else
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MERGES_OPTION=--no-merges
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fi
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SHORTUPSTREAM=$(git rev-parse --short $UPSTREAM)
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SHORTHEAD=$(git rev-parse --short $HEAD)
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@ -286,7 +390,7 @@ do
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# edit = use commit, but stop for amending
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# squash = use commit, but meld into previous commit
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EOF
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git rev-list --no-merges --pretty=oneline --abbrev-commit \
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git rev-list $MERGES_OPTION --pretty=oneline --abbrev-commit \
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--abbrev=7 --reverse $UPSTREAM..$HEAD | \
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sed "s/^/pick /" >> "$TODO"
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@ -166,4 +166,26 @@ test_expect_success 'retain authorship when squashing' '
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git show HEAD | grep "^Author: Nitfol"
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'
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test_expect_success 'preserve merges with -p' '
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git checkout -b to-be-preserved master^ &&
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: > unrelated-file &&
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git add unrelated-file &&
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test_tick &&
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git commit -m "unrelated" &&
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git checkout -b to-be-rebased master &&
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echo B > file1 &&
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test_tick &&
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git commit -m J file1 &&
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test_tick &&
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git merge to-be-preserved &&
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echo C > file1 &&
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test_tick &&
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git commit -m K file1 &&
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git rebase -i -p --onto branch1 master &&
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test $(git rev-parse HEAD^^2) = $(git rev-parse to-be-preserved) &&
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test $(git rev-parse HEAD~3) = $(git rev-parse branch1) &&
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test $(git show HEAD:file1) = C &&
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test $(git show HEAD~2:file1) = B
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'
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test_done
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