Build in merge

Mentored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 554 insertions, 0 deletions

diff --git a/contrib/examples/git-merge.sh b/contrib/examples/git-merge.sh
new file mode 100755
index 0000000000..8026ccff4a
--- /dev/null
+++ b/contrib/examples/git-merge.sh
@@ -0,0 +1,554 @@
+#!/bin/sh
+#
+# Copyright (c) 2005 Junio C Hamano
+#
+
+OPTIONS_KEEPDASHDASH=
+OPTIONS_SPEC="\
+git-merge [options] <remote>...
+git-merge [options] <msg> HEAD <remote>
+--
+stat                 show a diffstat at the end of the merge
+n                    don't show a diffstat at the end of the merge
+summary              (synonym to --stat)
+log                  add list of one-line log to merge commit message
+squash               create a single commit instead of doing a merge
+commit               perform a commit if the merge succeeds (default)
+ff                   allow fast forward (default)
+s,strategy=          merge strategy to use
+m,message=           message to be used for the merge commit (if any)
+"
+
+SUBDIRECTORY_OK=Yes
+. git-sh-setup
+require_work_tree
+cd_to_toplevel
+
+test -z "$(git ls-files -u)" ||
+	die "You are in the middle of a conflicted merge."
+
+LF='
+'
+
+all_strategies='recur recursive octopus resolve stupid ours subtree'
+default_twohead_strategies='recursive'
+default_octopus_strategies='octopus'
+no_fast_forward_strategies='subtree ours'
+no_trivial_strategies='recursive recur subtree ours'
+use_strategies=
+
+allow_fast_forward=t
+allow_trivial_merge=t
+squash= no_commit= log_arg=
+
+dropsave() {
+	rm -f -- "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/MERGE_MSG" \
+		 "$GIT_DIR/MERGE_STASH" || exit 1
+}
+
+savestate() {
+	# Stash away any local modifications.
+	git stash create >"$GIT_DIR/MERGE_STASH"
+}
+
+restorestate() {
+        if test -f "$GIT_DIR/MERGE_STASH"
+	then
+		git reset --hard $head >/dev/null
+		git stash apply $(cat "$GIT_DIR/MERGE_STASH")
+		git update-index --refresh >/dev/null
+	fi
+}
+
+finish_up_to_date () {
+	case "$squash" in
+	t)
+		echo "$1 (nothing to squash)" ;;
+	'')
+		echo "$1" ;;
+	esac
+	dropsave
+}
+
+squash_message () {
+	echo Squashed commit of the following:
+	echo
+	git log --no-merges --pretty=medium ^"$head" $remoteheads
+}
+
+finish () {
+	if test '' = "$2"
+	then
+		rlogm="$GIT_REFLOG_ACTION"
+	else
+		echo "$2"
+		rlogm="$GIT_REFLOG_ACTION: $2"
+	fi
+	case "$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 -m "$rlogm" HEAD "$1" "$head" || exit 1
+			git gc --auto
+			;;
+		esac
+		;;
+	esac
+	case "$1" in
+	'')
+		;;
+	?*)
+		if test "$show_diffstat" = t
+		then
+			# We want color (if set), but no pager
+			GIT_PAGER='' git diff --stat --summary -M "$head" "$1"
+		fi
+		;;
+	esac
+
+	# Run a post-merge hook
+        if test -x "$GIT_DIR"/hooks/post-merge
+        then
+	    case "$squash" in
+	    t)
+                "$GIT_DIR"/hooks/post-merge 1
+		;;
+	    '')
+                "$GIT_DIR"/hooks/post-merge 0
+		;;
+	    esac
+        fi
+}
+
+merge_name () {
+	remote="$1"
+	rh=$(git rev-parse --verify "$remote^0" 2>/dev/null) || return
+	bh=$(git show-ref -s --verify "refs/heads/$remote" 2>/dev/null)
+	if test "$rh" = "$bh"
+	then
+		echo "$rh		branch '$remote' of ."
+	elif truname=$(expr "$remote" : '\(.*\)~[1-9][0-9]*$') &&
+		git show-ref -q --verify "refs/heads/$truname" 2>/dev/null
+	then
+		echo "$rh		branch '$truname' (early part) of ."
+	elif test "$remote" = "FETCH_HEAD" -a -r "$GIT_DIR/FETCH_HEAD"
+	then
+		sed -e 's/	not-for-merge	/		/' -e 1q \
+			"$GIT_DIR/FETCH_HEAD"
+	else
+		echo "$rh		commit '$remote'"
+	fi
+}
+
+parse_config () {
+	while test $# != 0; do
+		case "$1" in
+		-n|--no-stat|--no-summary)
+			show_diffstat=false ;;
+		--stat|--summary)
+			show_diffstat=t ;;
+		--log|--no-log)
+			log_arg=$1 ;;
+		--squash)
+			test "$allow_fast_forward" = t ||
+				die "You cannot combine --squash with --no-ff."
+			squash=t no_commit=t ;;
+		--no-squash)
+			squash= no_commit= ;;
+		--commit)
+			no_commit= ;;
+		--no-commit)
+			no_commit=t ;;
+		--ff)
+			allow_fast_forward=t ;;
+		--no-ff)
+			test "$squash" != t ||
+				die "You cannot combine --squash with --no-ff."
+			allow_fast_forward=f ;;
+		-s|--strategy)
+			shift
+			case " $all_strategies " in
+			*" $1 "*)
+				use_strategies="$use_strategies$1 " ;;
+			*)
+				die "available strategies are: $all_strategies" ;;
+			esac
+			;;
+		-m|--message)
+			shift
+			merge_msg="$1"
+			have_message=t
+			;;
+		--)
+			shift
+			break ;;
+		*)	usage ;;
+		esac
+		shift
+	done
+	args_left=$#
+}
+
+test $# != 0 || usage
+
+have_message=
+
+if branch=$(git-symbolic-ref -q HEAD)
+then
+	mergeopts=$(git config "branch.${branch#refs/heads/}.mergeoptions")
+	if test -n "$mergeopts"
+	then
+		parse_config $mergeopts --
+	fi
+fi
+
+parse_config "$@"
+while test $args_left -lt $#; do shift; done
+
+if test -z "$show_diffstat"; then
+    test "$(git config --bool merge.diffstat)" = false && show_diffstat=false
+    test "$(git config --bool merge.stat)" = false && show_diffstat=false
+    test -z "$show_diffstat" && show_diffstat=t
+fi
+
+# This could be traditional "merge <msg> HEAD <commit>..."  and the
+# way we can tell it is to see if the second token is HEAD, but some
+# people might have misused the interface and used a committish that
+# is the same as HEAD there instead.  Traditional format never would
+# have "-m" so it is an additional safety measure to check for it.
+
+if test -z "$have_message" &&
+	second_token=$(git rev-parse --verify "$2^0" 2>/dev/null) &&
+	head_commit=$(git rev-parse --verify "HEAD" 2>/dev/null) &&
+	test "$second_token" = "$head_commit"
+then
+	merge_msg="$1"
+	shift
+	head_arg="$1"
+	shift
+elif ! git rev-parse --verify HEAD >/dev/null 2>&1
+then
+	# If the merged head is a valid one there is no reason to
+	# forbid "git merge" into a branch yet to be born.  We do
+	# the same for "git pull".
+	if test 1 -ne $#
+	then
+		echo >&2 "Can merge only exactly one commit into empty head"
+		exit 1
+	fi
+
+	rh=$(git rev-parse --verify "$1^0") ||
+		die "$1 - not something we can merge"
+
+	git update-ref -m "initial pull" HEAD "$rh" "" &&
+	git read-tree --reset -u HEAD
+	exit
+
+else
+	# We are invoked directly as the first-class UI.
+	head_arg=HEAD
+
+	# All the rest are the commits being merged; prepare
+	# the standard merge summary message to be appended to
+	# the given message.  If remote is invalid we will die
+	# later in the common codepath so we discard the error
+	# in this loop.
+	merge_name=$(for remote
+		do
+			merge_name "$remote"
+		done | git fmt-merge-msg $log_arg
+	)
+	merge_msg="${merge_msg:+$merge_msg$LF$LF}$merge_name"
+fi
+head=$(git rev-parse --verify "$head_arg"^0) || usage
+
+# All the rest are remote heads
+test "$#" = 0 && usage ;# we need at least one remote head.
+set_reflog_action "merge $*"
+
+remoteheads=
+for remote
+do
+	remotehead=$(git rev-parse --verify "$remote"^0 2>/dev/null) ||
+	    die "$remote - not something we can merge"
+	remoteheads="${remoteheads}$remotehead "
+	eval GITHEAD_$remotehead='"$remote"'
+	export GITHEAD_$remotehead
+done
+set x $remoteheads ; shift
+
+case "$use_strategies" in
+'')
+	case "$#" in
+	1)
+		var="`git config --get pull.twohead`"
+		if test -n "$var"
+		then
+			use_strategies="$var"
+		else
+			use_strategies="$default_twohead_strategies"
+		fi ;;
+	*)
+		var="`git config --get pull.octopus`"
+		if test -n "$var"
+		then
+			use_strategies="$var"
+		else
+			use_strategies="$default_octopus_strategies"
+		fi ;;
+	esac
+	;;
+esac
+
+for s in $use_strategies
+do
+	for ss in $no_fast_forward_strategies
+	do
+		case " $s " in
+		*" $ss "*)
+			allow_fast_forward=f
+			break
+			;;
+		esac
+	done
+	for ss in $no_trivial_strategies
+	do
+		case " $s " in
+		*" $ss "*)
+			allow_trivial_merge=f
+			break
+			;;
+		esac
+	done
+done
+
+case "$#" in
+1)
+	common=$(git merge-base --all $head "$@")
+	;;
+*)
+	common=$(git show-branch --merge-base $head "$@")
+	;;
+esac
+echo "$head" >"$GIT_DIR/ORIG_HEAD"
+
+case "$allow_fast_forward,$#,$common,$no_commit" in
+?,*,'',*)
+	# No common ancestors found. We need a real merge.
+	;;
+?,1,"$1",*)
+	# If head can reach all the merge then we are up to date.
+	# but first the most common case of merging one remote.
+	finish_up_to_date "Already up-to-date."
+	exit 0
+	;;
+t,1,"$head",*)
+	# Again the most common case of merging one remote.
+	echo "Updating $(git rev-parse --short $head)..$(git rev-parse --short $1)"
+	git update-index --refresh 2>/dev/null
+	msg="Fast forward"
+	if test -n "$have_message"
+	then
+		msg="$msg (no commit created; -m option ignored)"
+	fi
+	new_head=$(git rev-parse --verify "$1^0") &&
+	git read-tree -v -m -u --exclude-per-directory=.gitignore $head "$new_head" &&
+	finish "$new_head" "$msg" || exit
+	dropsave
+	exit 0
+	;;
+?,1,?*"$LF"?*,*)
+	# We are not doing octopus and not fast forward.  Need a
+	# real merge.
+	;;
+?,1,*,)
+	# We are not doing octopus, not fast forward, and have only
+	# one common.
+	git update-index --refresh 2>/dev/null
+	case "$allow_trivial_merge" in
+	t)
+		# See if it is really trivial.
+		git var GIT_COMMITTER_IDENT >/dev/null || exit
+		echo "Trying really trivial in-index merge..."
+		if git read-tree --trivial -m -u -v $common $head "$1" &&
+		   result_tree=$(git write-tree)
+		then
+			echo "Wonderful."
+			result_commit=$(
+				printf '%s\n' "$merge_msg" |
+				git commit-tree $result_tree -p HEAD -p "$1"
+			) || exit
+			finish "$result_commit" "In-index merge"
+			dropsave
+			exit 0
+		fi
+		echo "Nope."
+	esac
+	;;
+*)
+	# 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_STASH"
+    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 '' != "$result_tree"
+then
+    if test "$allow_fast_forward" = "t"
+    then
+        parents=$(git show-branch --independent "$head" "$@")
+    else
+        parents=$(git rev-parse "$head" "$@")
+    fi
+    parents=$(echo "$parents" | sed -e 's/^/-p /')
+    result_commit=$(printf '%s\n' "$merge_msg" | git commit-tree $result_tree $parents) || exit
+    finish "$result_commit" "Merge 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
+	case "$use_strategies" in
+	?*' '?*)
+		echo >&2 "No merge strategy handled the merge."
+		;;
+	*)
+		echo >&2 "Merge with strategy $use_strategies failed."
+		;;
+	esac
+	exit 2
+	;;
+"$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"
+	printf '%s\n' "$merge_msg" >"$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"
+	git rerere
+	die "Automatic merge failed; fix conflicts and then commit the result."
+fi