Multi-backend merge driver.

The new command 'git merge' takes the current head and one or more
remote heads, with the commit log message for the automated case.

If the heads being merged are simple fast-forwards, it acts the
same way as the current 'git resolve'.  Otherwise, it tries
different merge strategies and takes the result from the one that
succeeded auto-merging, if there is any.

If no merge strategy succeeds auto-merging, their results are
evaluated for number of paths needed for hand resolving, and the
one with the least number of such paths is left in the working
tree.  The user is asked to resolve them by hand and make a
commit manually.

The calling convention from the 'git merge' driver to merge
strategy programs is very simple:

 - A strategy program is to be called 'git-merge-<strategy>'.

 - They take input of this form:

	<common1> <common2> ... '--' <head> <remote1> <remote2>...

   That is, one or more the common ancestors, double dash, the
   current head, and one or more remote heads being merged into
   the current branch.

 - Before a strategy program is called, the working tree is
   matched to the current <head>.

 - The strategy program exits with status code 0 when it
   successfully auto-merges the given heads.  It should do
   update-cache for all the merged paths when it does so -- the
   index file will be used to record the merge result as a
   commit by the driver.

 - The strategy program exits with status code 1 when it leaves
   conflicts behind.  It should do update-cache for all the
   merged paths that it successfully auto-merged, and leave the
   cache entry in the index file as the same as <head> for paths
   it could not auto-merge, and leave its best-effort result
   with conflict markers in the working tree when it does so.

 - The strategy program exists with status code other than 0 or
   1 if it does not handle the given merge at all.

As examples, this commit comes with merge strategies based on
'git resolve' and 'git octopus'.

Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Junio C Hamano 2005-09-08 13:47:12 -07:00
parent bb97a2a804
commit 91063bbc6c
5 changed files with 381 additions and 2 deletions

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@ -73,7 +73,8 @@ SCRIPT_SH = \
git-repack.sh git-request-pull.sh git-reset.sh \ git-repack.sh git-request-pull.sh git-reset.sh \
git-resolve.sh git-revert.sh git-sh-setup.sh git-status.sh \ git-resolve.sh git-revert.sh git-sh-setup.sh git-status.sh \
git-tag.sh git-verify-tag.sh git-whatchanged.sh git.sh \ git-tag.sh git-verify-tag.sh git-whatchanged.sh git.sh \
git-applymbox.sh git-applypatch.sh git-applymbox.sh git-applypatch.sh \
git-merge.sh git-merge-resolve.sh git-merge-octopus.sh
SCRIPT_PERL = \ SCRIPT_PERL = \
git-archimport.perl git-cvsimport.perl git-relink.perl \ git-archimport.perl git-cvsimport.perl git-relink.perl \

View File

@ -158,7 +158,7 @@ if [ ! -r "$GIT_DIR/HEAD" ]; then
PARENTS="" PARENTS=""
else else
if [ -f "$GIT_DIR/MERGE_HEAD" ]; then if [ -f "$GIT_DIR/MERGE_HEAD" ]; then
PARENTS="-p HEAD -p MERGE_HEAD" PARENTS="-p HEAD "`sed -e 's/^/-p /' "$GIT_DIR/MERGE_HEAD"`
fi fi
if test "$use_commit" != "" if test "$use_commit" != ""
then then

86
git-merge-octopus.sh Executable file
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@ -0,0 +1,86 @@
#!/bin/sh
#
# Copyright (c) 2005 Junio C Hamano
#
# Resolve two or more trees.
#
# The first parameters up to -- are merge bases; the rest are heads.
bases= head= remotes= sep_seen=
for arg
do
case ",$sep_seen,$head,$arg," in
*,--,)
sep_seen=yes
;;
,yes,,*)
head=$arg
;;
,yes,*)
remotes="$remotes$arg "
;;
*)
bases="$bases$arg "
;;
esac
done
# Reject if this is not an Octopus -- resolve should be used instead.
case "$remotes" in
?*' '?*)
;;
*)
exit 2 ;;
esac
# MRC is the current "merge reference commit"
# MRT is the current "merge result tree"
MRC=$head MSG= PARENT="-p $head"
MRT=$(git-write-tree)
CNT=1 ;# counting our head
NON_FF_MERGE=0
for SHA1 in $remotes
do
common=$(git-merge-base $MRC $SHA1) ||
die "Unable to find common commit with $SHA1"
if test "$common" = $SHA1
then
echo "Already up-to-date with $SHA1"
continue
fi
CNT=`expr $CNT + 1`
PARENT="$PARENT -p $SHA1"
if test "$common,$NON_FF_MERGE" = "$MRC,0"
then
# The first head being merged was a fast-forward.
# Advance MRC to the head being merged, and use that
# tree as the intermediate result of the merge.
# We still need to count this as part of the parent set.
echo "Fast forwarding to: $SHA1"
git-read-tree -u -m $head $SHA1 || exit
MRC=$SHA1 MRT=$(git-write-tree)
continue
fi
NON_FF_MERGE=1
echo "Trying simple merge with $SHA1"
git-read-tree -u -m $common $MRT $SHA1 || exit 2
next=$(git-write-tree 2>/dev/null)
if test $? -ne 0
then
echo "Simple merge did not work, trying automatic merge."
git-merge-index -o git-merge-one-file -a ||
exit 2 ; # Automatic merge failed; should not be doing Octopus
next=$(git-write-tree 2>/dev/null)
fi
MRC=$common
MRT=$next
done
exit 0

80
git-merge-resolve.sh Executable file
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@ -0,0 +1,80 @@
#!/bin/sh
#
# Copyright (c) 2005 Linus Torvalds
#
# Resolve two trees.
# The first parameters up to -- are merge bases; the rest are heads.
bases= head= remotes= sep_seen=
for arg
do
case ",$sep_seen,$head,$arg," in
*,--,)
sep_seen=yes
;;
,yes,,*)
head=$arg
;;
,yes,*)
remotes="$remotes$arg "
;;
*)
bases="$bases$arg "
;;
esac
done
# Give up if we are given more than two remotes -- not handling octopus.
case "$remotes" in
?*' '?*)
exit 2 ;;
esac
# Find an optimum merge base if there are more than one candidates.
case "$bases" in
?*' '?*)
echo "Trying to find the optimum merge base."
G=.tmp-index$$
best=
best_cnt=-1
for c in $bases
do
rm -f $G
GIT_INDEX_FILE=$G git-read-tree -m $c $head $remotes \
2>/dev/null || continue
# Count the paths that are unmerged.
cnt=`GIT_INDEX_FILE=$G git-ls-files --unmerged | wc -l`
if test $best_cnt -le 0 -o $cnt -le $best_cnt
then
best=$c
best_cnt=$cnt
if test "$best_cnt" -eq 0
then
# Cannot do any better than all trivial merge.
break
fi
fi
done
rm -f $G
common="$best"
;;
*)
common="$bases"
;;
esac
git-update-index --refresh 2>/dev/null
git-read-tree -u -m $common $head $remotes || exit 2
echo "Trying simple merge."
if result_tree=$(git-write-tree 2>/dev/null)
then
exit 0
else
echo "Simple merge failed, trying Automatic merge."
if git-merge-index -o git-merge-one-file -a
then
exit 0
else
exit 1
fi
fi

212
git-merge.sh Executable file
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@ -0,0 +1,212 @@
#!/bin/sh
#
# Copyright (c) 2005 Junio C Hamano
#
. git-sh-setup || die "Not a git archive"
LF='
'
usage () {
die "git-merge [-n] [-s <strategy>]... <merge-message> <head> <remote>+"
}
# all_strategies='resolve multibase fredrik octopus'
all_strategies='resolve multibase octopus'
default_strategies='resolve multibase octopus'
use_strategies=
dropheads() {
rm -f -- "$GIT_DIR/MERGE_HEAD" || exit 1
}
summary() {
case "$no_summary" in
'')
git-diff-tree -p -M $head "$1" |
git-apply --stat --summary
;;
esac
}
while case "$#" in 0) break ;; esac
do
case "$1" in
-n|--n|--no|--no-|--no-s|--no-su|--no-sum|--no-summ|\
--no-summa|--no-summar|--no-summary)
no_summary=t ;;
-s=*|--s=*|--st=*|--str=*|--stra=*|--strat=*|--strate=*|\
--strateg=*|--strategy=*|\
-s|--s|--st|--str|--stra|--strat|--strate|--strateg|--strategy)
case "$#,$1" in
*,*=*)
strategy=`expr "$1" : '-[^=]*=\(.*\)'` ;;
0,*)
usage ;;
*)
strategy="$2"
shift ;;
esac
case " $all_strategies " in
*" $strategy "*)
use_strategies="$use_strategies$strategy " ;;
*)
die "available strategies are: $all_strategies" ;;
esac
;;
-*) usage ;;
*) break ;;
esac
shift
done
case "$use_strategies" in
'')
use_strategies=$default_strategies
;;
esac
test "$#" -le 2 && usage ;# we need at least two heads.
merge_msg="$1"
shift
head=$(git-rev-parse --verify "$1"^0) || usage
shift
# All the rest are remote heads
for remote
do
git-rev-parse --verify "$remote"^0 >/dev/null ||
die "$remote - not something we can merge"
done
common=$(git-show-branch --merge-base $head "$@")
echo "$head" >"$GIT_DIR/ORIG_HEAD"
case "$#,$common" in
*,'')
die "Unable to find common commit between $head and $*"
;;
1,"$1")
# If head can reach all the merge then we are up to date.
# but first the most common case of merging one remote
echo "Already up-to-date. Yeeah!"
dropheads
exit 0
;;
1,"$head")
# Again the most common case of merging one remote.
echo "Updating from $head to $1."
git-update-index --refresh 2>/dev/null
git-read-tree -u -m $head "$1" || exit 1
git-rev-parse --verify "$1^0" > "$GIT_DIR/HEAD"
summary "$1"
dropheads
exit 0
;;
1,*)
# We are not doing octopus and not fast forward. Need a
# real merge.
;;
*)
# An octopus. If we can reach all the remote we are up to date.
up_to_date=t
for remote
do
common_one=$(git-merge-base $head $remote)
if test "$common_one" != "$remote"
then
up_to_date=f
break
fi
done
if test "$up_to_date" = t
then
echo "Already up-to-date. Yeeah!"
dropheads
exit 0
fi
;;
esac
# At this point we need a real merge. Require that the tree matches
# exactly our head.
git-update-index --refresh &&
test '' = "`git-diff-index --cached --name-only $head`" || {
die "Need real merge but the working tree has local changes."
}
result_tree= best_cnt=-1 best_strategy= wt_strategy=
for strategy in $use_strategies
do
test "$wt_strategy" = '' || {
echo "Rewinding the tree to pristine..."
git reset --hard $head
}
echo "Trying merge strategy $strategy..."
wt_strategy=$strategy
git-merge-$strategy $common -- $head "$@" || {
# The backend exits with 1 when conflicts are left to be resolved,
# with 2 when it does not handle the given merge at all.
exit=$?
if test "$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="-p $head"
for remote
do
parents="$parents -p $remote"
done
result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents)
echo "Committed merge $result_commit, made by $wt_strategy."
echo $result_commit >"$GIT_DIR/HEAD"
summary $result_commit
dropheads
exit 0
fi
# Pick the result from the best strategy and have the user fix it up.
case "$best_strategy" in
'')
git reset --hard $head
die "No merge strategy handled the merge."
;;
"$wt_strategy")
# We already have its result in the working tree.
;;
*)
echo "Rewinding the tree to pristine..."
git reset --hard $head
echo "Using the $best_strategy to prepare resolving by hand."
git-merge-$best_strategy $common -- $head "$@"
;;
esac
for remote
do
echo $remote
done >"$GIT_DIR/MERGE_HEAD"
die "Automatic merge failed; fix up by hand"