Teach 'git pull' about --rebase

When calling 'git pull' with the '--rebase' option, it performs a
fetch + rebase instead of a fetch + merge.

This behavior is more desirable than fetch + pull when a topic branch
is ready to be submitted and needs to be update.

fetch + rebase might also be considered a better workflow with shared
repositories in any case, or for contributors to a centrally managed
repository, such as WINE's.

As a convenience, you can set the default behavior for a branch by
defining the config variable branch.<name>.rebase, which is
interpreted as a bool.  This setting can be overridden on the command
line by --rebase and --no-rebase.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -346,6 +346,13 @@ branch.<name>.mergeoptions::
 	option values containing whitespace characters are currently not
 	supported.
 
+branch.<name>.rebase::
+	When true, rebase the branch <name> on top of the fetched branch,
+	instead of merging the default branch from the default remote.
+	*NOTE*: this is a possibly dangerous operation; do *not* use
+	it unless you understand the implications (see gitlink:git-rebase[1]
+	for details).
+
 clean.requireForce::
 	A boolean to make git-clean do nothing unless given -f
 	or -n.   Defaults to true.

Documentation/git-pull.txt

@@ -33,6 +33,16 @@ include::urls-remotes.txt[]
 
 include::merge-strategies.txt[]
 
+\--rebase::
+	Instead of a merge, perform a rebase after fetching.
+	*NOTE:* This is a potentially _dangerous_ mode of operation.
+	It rewrites history, which does not bode well when you
+	published that history already.  Do *not* use this option
+	unless you have read gitlink:git-rebase[1] carefully.
+
+\--no-rebase::
+	Override earlier \--rebase.
+
 DEFAULT BEHAVIOUR
 -----------------
 

git-pull.sh

@@ -17,6 +17,9 @@ test -z "$(git ls-files -u)" ||
 	die "You are in the middle of a conflicted merge."
 
 strategy_args= no_summary= no_commit= squash= no_ff=
+curr_branch=$(git symbolic-ref -q HEAD)
+curr_branch_short=$(echo "$curr_branch" | sed "s|refs/heads/||")
+rebase=$(git config --bool branch.$curr_branch_short.rebase)
 while :
 do
 	case "$1" in
@@ -52,6 +55,12 @@ do
 		esac
 		strategy_args="${strategy_args}-s $strategy "
 		;;
+	-r|--r|--re|--reb|--reba|--rebas|--rebase)
+		rebase=true
+		;;
+	--no-r|--no-re|--no-reb|--no-reba|--no-rebas|--no-rebase)
+		rebase=false
+		;;
 	-h|--h|--he|--hel|--help)
 		usage
 		;;
@@ -95,7 +104,6 @@ merge_head=$(sed -e '/	not-for-merge	/d' \
 
 case "$merge_head" in
 '')
-	curr_branch=$(git symbolic-ref -q HEAD)
 	case $? in
 	  0) ;;
 	  1) echo >&2 "You are not currently on a branch; you must explicitly"
@@ -142,5 +150,6 @@ then
 fi
 
 merge_name=$(git fmt-merge-msg <"$GIT_DIR/FETCH_HEAD") || exit
+test true = "$rebase" && exec git-rebase $merge_head
 exec git-merge $no_summary $no_commit $squash $no_ff $strategy_args \
 	"$merge_name" HEAD $merge_head

t/t5520-pull.sh

@@ -53,4 +53,26 @@ test_expect_success 'the default remote . should not break explicit pull' '
 	test `cat file` = modified
 '
 
+test_expect_success '--rebase' '
+	git branch to-rebase &&
+	echo modified again > file &&
+	git commit -m file file &&
+	git checkout to-rebase &&
+	echo new > file2 &&
+	git add file2 &&
+	git commit -m "new file" &&
+	git tag before-rebase &&
+	git pull --rebase . copy &&
+	test $(git rev-parse HEAD^) = $(git rev-parse copy) &&
+	test new = $(git show HEAD:file2)
+'
+
+test_expect_success 'branch.to-rebase.rebase' '
+	git reset --hard before-rebase &&
+	git config branch.to-rebase.rebase 1 &&
+	git pull . copy &&
+	test $(git rev-parse HEAD^) = $(git rev-parse copy) &&
+	test new = $(git show HEAD:file2)
+'
+
 test_done