git/git-merge.sh
Junio C Hamano 7d0c68871a git-merge --squash
Some people tend to do many little commits on a topic branch,
recording all the trials and errors, and when the topic is
reasonably cooked well, would want to record the net effect of
the series as one commit on top of the mainline, removing the
cruft from the history.  The topic is then abandoned or forked
off again from that point at the mainline.

The barebone porcelainish that comes with core git tools does
not officially support such operation, but you can fake it by
using "git pull --no-merge" when such a topic branch is not a
strict superset of the mainline, like this:

	git checkout mainline
	git pull --no-commit . that-topic-branch
	: fix conflicts if any
	rm -f .git/MERGE_HEAD
        git commit -a -m 'consolidated commit log message'
	git branch -f that-topic-branch ;# now fully merged

This however does not work when the topic branch is a fast
forward of the mainline, because normal "git pull" will never
create a merge commit in such a case, and there is nothing
special --no-commit could do to begin with.

This patch introduces a new option, --squash, to support such a
workflow officially in both fast-forward case and true merge
case.  The user-level operation would be the same in both cases:

	git checkout mainline
        git pull --squash . that-topic-branch
        : fix conflicts if any -- naturally, there would be
        : no conflict if fast forward.
	git commit -a -m  'consolidated commit log message'
	git branch -f that-topic-branch ;# now fully merged

When the current branch is already up-to-date with respect to
the other branch, there truly is nothing to do, so the new
option does not have any effect.

This was brought up in #git IRC channel recently.

Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-06-24 01:11:19 -07:00

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#!/bin/sh
#
# Copyright (c) 2005 Junio C Hamano
#
USAGE='[-n] [--no-commit] [--squash] [-s <strategy>]... <merge-message> <head> <remote>+'
. git-sh-setup
LF='
'
all_strategies='recursive octopus resolve stupid ours'
default_twohead_strategies='recursive'
default_octopus_strategies='octopus'
no_trivial_merge_strategies='ours'
use_strategies=
index_merge=t
if test "@@NO_PYTHON@@"; then
all_strategies='resolve octopus stupid ours'
default_twohead_strategies='resolve'
fi
dropsave() {
rm -f -- "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/MERGE_MSG" \
"$GIT_DIR/MERGE_SAVE" || exit 1
}
savestate() {
# Stash away any local modifications.
git-diff-index -z --name-only $head |
cpio -0 -o >"$GIT_DIR/MERGE_SAVE"
}
restorestate() {
if test -f "$GIT_DIR/MERGE_SAVE"
then
git reset --hard $head
cpio -iuv <"$GIT_DIR/MERGE_SAVE"
git-update-index --refresh >/dev/null
fi
}
finish_up_to_date () {
case "$squash" in
t)
echo "$1 (nothing to squash)" ;;
'')
echo "$1" ;;
esac
dropsave
}
squash_message () {
echo Squashed commit of the following:
echo
git-log --no-merges ^"$head" $remote
}
finish () {
test '' = "$2" || echo "$2"
case "$squash" in
t)
echo "Squash commit -- not updating HEAD"
squash_message >"$GIT_DIR/SQUASH_MSG"
;;
'')
case "$merge_msg" in
'')
echo "No merge message -- not updating HEAD"
;;
*)
git-update-ref HEAD "$1" "$head" || exit 1
;;
esac
;;
esac
case "$1" in
'')
;;
?*)
case "$no_summary" in
'')
git-diff-tree --stat --summary -M "$head" "$1"
;;
esac
;;
esac
}
while case "$#" in 0) break ;; esac
do
case "$1" in
-n|--n|--no|--no-|--no-s|--no-su|--no-sum|--no-summ|\
--no-summa|--no-summar|--no-summary)
no_summary=t ;;
--sq|--squ|--squa|--squas|--squash)
squash=t no_commit=t ;;
--no-c|--no-co|--no-com|--no-comm|--no-commi|--no-commit)
no_commit=t ;;
-s=*|--s=*|--st=*|--str=*|--stra=*|--strat=*|--strate=*|\
--strateg=*|--strategy=*|\
-s|--s|--st|--str|--stra|--strat|--strate|--strateg|--strategy)
case "$#,$1" in
*,*=*)
strategy=`expr "$1" : '-[^=]*=\(.*\)'` ;;
1,*)
usage ;;
*)
strategy="$2"
shift ;;
esac
case " $all_strategies " in
*" $strategy "*)
use_strategies="$use_strategies$strategy " ;;
*)
die "available strategies are: $all_strategies" ;;
esac
;;
-*) usage ;;
*) break ;;
esac
shift
done
merge_msg="$1"
shift
head_arg="$1"
head=$(git-rev-parse --verify "$1"^0) || usage
shift
# All the rest are remote heads
test "$#" = 0 && usage ;# we need at least one remote head.
remoteheads=
for remote
do
remotehead=$(git-rev-parse --verify "$remote"^0) ||
die "$remote - not something we can merge"
remoteheads="${remoteheads}$remotehead "
done
set x $remoteheads ; shift
case "$use_strategies" in
'')
case "$#" in
1)
use_strategies="$default_twohead_strategies" ;;
*)
use_strategies="$default_octopus_strategies" ;;
esac
;;
esac
for s in $use_strategies
do
case " $s " in
*" $no_trivial_merge_strategies "*)
index_merge=f
break
;;
esac
done
case "$#" in
1)
common=$(git-merge-base --all $head "$@")
;;
*)
common=$(git-show-branch --merge-base $head "$@")
;;
esac
echo "$head" >"$GIT_DIR/ORIG_HEAD"
case "$index_merge,$#,$common,$no_commit" in
f,*)
# We've been told not to try anything clever. Skip to real merge.
;;
?,*,'',*)
# No common ancestors found. We need a real merge.
;;
?,1,"$1",*)
# If head can reach all the merge then we are up to date.
# but first the most common case of merging one remote.
finish_up_to_date "Already up-to-date."
exit 0
;;
?,1,"$head",*)
# Again the most common case of merging one remote.
echo "Updating from $head to $1"
git-update-index --refresh 2>/dev/null
new_head=$(git-rev-parse --verify "$1^0") &&
git-read-tree -u -v -m $head "$new_head" &&
finish "$new_head" "Fast forward"
dropsave
exit 0
;;
?,1,?*"$LF"?*,*)
# We are not doing octopus and not fast forward. Need a
# real merge.
;;
?,1,*,)
# We are not doing octopus, not fast forward, and have only
# one common. See if it is really trivial.
git var GIT_COMMITTER_IDENT >/dev/null || exit
echo "Trying really trivial in-index merge..."
git-update-index --refresh 2>/dev/null
if git-read-tree --trivial -m -u -v $common $head "$1" &&
result_tree=$(git-write-tree)
then
echo "Wonderful."
result_commit=$(
echo "$merge_msg" |
git-commit-tree $result_tree -p HEAD -p "$1"
) || exit
finish "$result_commit" "In-index merge"
dropsave
exit 0
fi
echo "Nope."
;;
*)
# An octopus. If we can reach all the remote we are up to date.
up_to_date=t
for remote
do
common_one=$(git-merge-base --all $head $remote)
if test "$common_one" != "$remote"
then
up_to_date=f
break
fi
done
if test "$up_to_date" = t
then
finish_up_to_date "Already up-to-date. Yeeah!"
exit 0
fi
;;
esac
# We are going to make a new commit.
git var GIT_COMMITTER_IDENT >/dev/null || exit
# At this point, we need a real merge. No matter what strategy
# we use, it would operate on the index, possibly affecting the
# working tree, and when resolved cleanly, have the desired tree
# in the index -- this means that the index must be in sync with
# the $head commit. The strategies are responsible to ensure this.
case "$use_strategies" in
?*' '?*)
# Stash away the local changes so that we can try more than one.
savestate
single_strategy=no
;;
*)
rm -f "$GIT_DIR/MERGE_SAVE"
single_strategy=yes
;;
esac
result_tree= best_cnt=-1 best_strategy= wt_strategy=
merge_was_ok=
for strategy in $use_strategies
do
test "$wt_strategy" = '' || {
echo "Rewinding the tree to pristine..."
restorestate
}
case "$single_strategy" in
no)
echo "Trying merge strategy $strategy..."
;;
esac
# Remember which strategy left the state in the working tree
wt_strategy=$strategy
git-merge-$strategy $common -- "$head_arg" "$@"
exit=$?
if test "$no_commit" = t && test "$exit" = 0
then
merge_was_ok=t
exit=1 ;# pretend it left conflicts.
fi
test "$exit" = 0 || {
# The backend exits with 1 when conflicts are left to be resolved,
# with 2 when it does not handle the given merge at all.
if test "$exit" -eq 1
then
cnt=`{
git-diff-files --name-only
git-ls-files --unmerged
} | wc -l`
if test $best_cnt -le 0 -o $cnt -le $best_cnt
then
best_strategy=$strategy
best_cnt=$cnt
fi
fi
continue
}
# Automerge succeeded.
result_tree=$(git-write-tree) && break
done
# If we have a resulting tree, that means the strategy module
# auto resolved the merge cleanly.
if test '' != "$result_tree"
then
parents=$(git-show-branch --independent "$head" "$@" | sed -e 's/^/-p /')
result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents) || exit
finish "$result_commit" "Merge $result_commit, made by $wt_strategy."
dropsave
exit 0
fi
# Pick the result from the best strategy and have the user fix it up.
case "$best_strategy" in
'')
restorestate
echo >&2 "No merge strategy handled the merge."
exit 2
;;
"$wt_strategy")
# We already have its result in the working tree.
;;
*)
echo "Rewinding the tree to pristine..."
restorestate
echo "Using the $best_strategy to prepare resolving by hand."
git-merge-$best_strategy $common -- "$head_arg" "$@"
;;
esac
if test "$squash" = t
then
finish
else
for remote
do
echo $remote
done >"$GIT_DIR/MERGE_HEAD"
echo "$merge_msg" >"$GIT_DIR/MERGE_MSG"
fi
if test "$merge_was_ok" = t
then
echo >&2 \
"Automatic merge went well; stopped before committing as requested"
exit 0
else
{
echo '
Conflicts:
'
git ls-files --unmerged |
sed -e 's/^[^ ]* / /' |
uniq
} >>"$GIT_DIR/MERGE_MSG"
if test -d "$GIT_DIR/rr-cache"
then
git-rerere
fi
die "Automatic merge failed; fix conflicts and then commit the result."
fi