[PATCH] pull: require choice between rebase/merge on non-fast-forward pull

[Junio C Hamano <gitster@pobox.com>]

Because letting a trivial merge automatically handled by Git is so
easy with "git pull", a person who is new to Git may not realize
that the project s/he is interacting with may prefer "rebase"
workflow.  Add a safety valve to fail "git pull" that is not a
fast-forward until/unless the user expressed her preference between
the two.

Those who want the existing behaviour could just do

    git config --global pull.rebase false

once, and they'd not even notice.

    http://thread.gmane.org/gmane.comp.version-control.git/225146/focus=225326

for a full discussion.

The fallout from this change to test suite is not very pretty, though.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * This is not a serious inclusion proposal yet, but to see if
   people are still interested in possibly helping new users.

 git-pull.sh                            | 36 +++++++++++++++++++++++++++++++++-
 t/annotate-tests.sh                    |  2 +-
 t/t4013-diff-various.sh                |  2 ++
 t/t4200-rerere.sh                      |  2 ++
 t/t5500-fetch-pack.sh                  |  6 +++++-
 t/t5521-pull-options.sh                |  2 ++
 t/t5524-pull-msg.sh                    |  2 +-
 t/t5700-clone-reference.sh             |  4 ++--
 t/t6022-merge-rename.sh                |  2 ++
 t/t6026-merge-attr.sh                  |  2 +-
 t/t6029-merge-subtree.sh               |  1 +
 t/t6037-merge-ours-theirs.sh           |  2 ++
 t/t9114-git-svn-dcommit-merge.sh       |  2 +-
 t/t9400-git-cvsserver-server.sh        |  2 +-
 t/t9500-gitweb-standalone-no-errors.sh |  2 +-
 15 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/git-pull.sh b/git-pull.sh
index 638aabb..4a6a863 100755
--- a/git-pull.sh
+++ b/git-pull.sh
@@ -41,13 +41,21 @@ test -f "$GIT_DIR/MERGE_HEAD" && die_merge
 strategy_args= diffstat= no_commit= squash= no_ff= ff_only=
 log_arg= verbosity= progress= recurse_submodules= verify_signatures=
 merge_args= edit=
+
 curr_branch=$(git symbolic-ref -q HEAD)
 curr_branch_short="${curr_branch#refs/heads/}"
+
+# See if we are configured to rebase by default.
+# The value $rebase is, throughout the main part of the code:
+#    (empty) - the user did not have any preference
+#    true    - the user told us to integrate by rebasing
+#    flase   - the user told us to integrate by merging
 rebase=$(git config --bool branch.$curr_branch_short.rebase)
 if test -z "$rebase"
 then
 	rebase=$(git config --bool pull.rebase)
 fi
+
 dry_run=
 while :
 do
@@ -113,7 +121,8 @@ do
 	-r|--r|--re|--reb|--reba|--rebas|--rebase)
 		rebase=true
 		;;
-	--no-r|--no-re|--no-reb|--no-reba|--no-rebas|--no-rebase)
+	--no-r|--no-re|--no-reb|--no-reba|--no-rebas|--no-rebase|\
+	-m|--m|--me|--mer|--merg|--merge)
 		rebase=false
 		;;
 	--recurse-submodules)
@@ -219,6 +228,7 @@ test true = "$rebase" && {
 		fi
 	done
 }
+
 orig_head=$(git rev-parse -q --verify HEAD)
 git fetch $verbosity $progress $dry_run $recurse_submodules --update-head-ok "$@" || exit 1
 test -z "$dry_run" || exit 0
@@ -264,6 +274,30 @@ case "$merge_head" in
 		die "$(gettext "Cannot rebase onto multiple branches")"
 	fi
 	;;
+*)
+	# integrating with a single other history
+	merge_head=${merge_head% }
+	if test -z "$rebase$no_ff$ff_only${squash#--no-squash}" &&
+		test -n "$orig_head" &&
+		! $(git merge-base --is-ancestor "$orig_head" "$merge_head")
+	then
+echo >&2 "orig-head was $orig_head"
+echo >&2 "merge-head is $merge_head"
+git show >&2 --oneline -s "$orig_head" "$merge_head"
+
+		die "The pull does not fast-forward; please specify
+if you want to merge or rebase.
+
+Use either
+
+    git pull --rebase
+    git pull --merge
+
+You can also use 'git config pull.rebase true' (if you want --rebase) or
+'git config pull.rebase false' (if you want --merge) to set this once for
+this project and forget about it."
+	fi
+	;;
 esac
 
 if test -z "$orig_head"
diff --git a/t/annotate-tests.sh b/t/annotate-tests.sh
index c56a77d..af02c6d 100644
--- a/t/annotate-tests.sh
+++ b/t/annotate-tests.sh
@@ -79,7 +79,7 @@ test_expect_success \
 
 test_expect_success \
     'merge-setup part 3' \
-    'git pull . branch1'
+    'git pull --merge . branch1'
 
 test_expect_success \
     'Two lines blamed on A, one on B, two on B1, one on B2' \
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index e77c09c..1ee2198 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -12,6 +12,8 @@ LF='
 
 test_expect_success setup '
 
+	git config pull.rebase false &&
+
 	GIT_AUTHOR_DATE="2006-06-26 00:00:00 +0000" &&
 	GIT_COMMITTER_DATE="2006-06-26 00:00:00 +0000" &&
 	export GIT_AUTHOR_DATE GIT_COMMITTER_DATE &&
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 7f6666f..0563357 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -25,6 +25,8 @@ test_description='git rerere
 . ./test-lib.sh
 
 test_expect_success 'setup' '
+	git config pull.rebase false &&
+
 	cat >a1 <<-\EOF &&
 	Some title
 	==========
diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index fd2598e..4be8877 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -143,7 +143,11 @@ test_expect_success 'clone shallow depth 1 with fsck' '
 '
 
 test_expect_success 'clone shallow' '
-	git clone --no-single-branch --depth 2 "file://$(pwd)/." shallow
+	git clone --no-single-branch --depth 2 "file://$(pwd)/." shallow &&
+	(
+		cd shallow &&
+		git config pull.rebase false
+	)
 '
 
 test_expect_success 'clone shallow depth count' '
diff --git a/t/t5521-pull-options.sh b/t/t5521-pull-options.sh
index 453aba5..d821fab 100755
--- a/t/t5521-pull-options.sh
+++ b/t/t5521-pull-options.sh
@@ -91,6 +91,8 @@ test_expect_success 'git pull --force' '
 	[branch "master"]
 		remote = two
 		merge = refs/heads/master
+	[pull]
+		rebase = false
 	EOF
 	git pull two &&
 	test_commit A &&
diff --git a/t/t5524-pull-msg.sh b/t/t5524-pull-msg.sh
index 8cccecc..660714b 100755
--- a/t/t5524-pull-msg.sh
+++ b/t/t5524-pull-msg.sh
@@ -25,7 +25,7 @@ test_expect_success setup '
 test_expect_success pull '
 (
 	cd cloned &&
-	git pull --log &&
+	git pull --log --merge &&
 	git log -2 &&
 	git cat-file commit HEAD >result &&
 	grep Dollar result
diff --git a/t/t5700-clone-reference.sh b/t/t5700-clone-reference.sh
index 6537911..306badf 100755
--- a/t/t5700-clone-reference.sh
+++ b/t/t5700-clone-reference.sh
@@ -94,7 +94,7 @@ cd "$base_dir"
 
 test_expect_success 'pulling changes from origin' \
 'cd C &&
-git pull origin'
+git pull --merge origin'
 
 cd "$base_dir"
 
@@ -109,7 +109,7 @@ cd "$base_dir"
 
 test_expect_success 'pulling changes from origin' \
 'cd D &&
-git pull origin'
+git pull --merge origin'
 
 cd "$base_dir"
 
diff --git a/t/t6022-merge-rename.sh b/t/t6022-merge-rename.sh
index c680f78..e12d90b 100755
--- a/t/t6022-merge-rename.sh
+++ b/t/t6022-merge-rename.sh
@@ -10,6 +10,8 @@ modify () {
 
 test_expect_success setup \
 '
+git config pull.rebase false &&
+
 cat >A <<\EOF &&
 a aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 b bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
diff --git a/t/t6026-merge-attr.sh b/t/t6026-merge-attr.sh
index 5e43997..5428f19 100755
--- a/t/t6026-merge-attr.sh
+++ b/t/t6026-merge-attr.sh
@@ -172,7 +172,7 @@ test_expect_success 'up-to-date merge without common ancestor' '
 	test_tick &&
 	(
 		cd repo1 &&
-		git pull ../repo2 master
+		git pull --merge ../repo2 master
 	)
 '
 
diff --git a/t/t6029-merge-subtree.sh b/t/t6029-merge-subtree.sh
index 73fc240..3ca29c4 100755
--- a/t/t6029-merge-subtree.sh
+++ b/t/t6029-merge-subtree.sh
@@ -41,6 +41,7 @@ test_expect_success 'setup' '
 	mkdir git &&
 	cd git &&
 	git init &&
+	git config pull.rebase false &&
 	echo git >git.c &&
 	o2=$(git hash-object git.c) &&
 	git add git.c &&
diff --git a/t/t6037-merge-ours-theirs.sh b/t/t6037-merge-ours-theirs.sh
index 3889eca..41bf060 100755
--- a/t/t6037-merge-ours-theirs.sh
+++ b/t/t6037-merge-ours-theirs.sh
@@ -66,6 +66,8 @@ test_expect_success 'binary file with -Xours/-Xtheirs' '
 '
 
 test_expect_success 'pull passes -X to underlying merge' '
+	git config pull.rebase false &&
+
 	git reset --hard master && git pull -s recursive -Xours . side &&
 	git reset --hard master && git pull -s recursive -X ours . side &&
 	git reset --hard master && git pull -s recursive -Xtheirs . side &&
diff --git a/t/t9114-git-svn-dcommit-merge.sh b/t/t9114-git-svn-dcommit-merge.sh
index f524d2f..dfce024 100755
--- a/t/t9114-git-svn-dcommit-merge.sh
+++ b/t/t9114-git-svn-dcommit-merge.sh
@@ -62,7 +62,7 @@ test_expect_success 'setup git mirror and merge' '
 	echo friend > README &&
 	cat tmp >> README &&
 	git commit -a -m "friend" &&
-	git pull . merge
+	git pull --merge . merge
 	'
 
 test_debug 'gitk --all & sleep 1'
diff --git a/t/t9400-git-cvsserver-server.sh b/t/t9400-git-cvsserver-server.sh
index 0431386..76b8640 100755
--- a/t/t9400-git-cvsserver-server.sh
+++ b/t/t9400-git-cvsserver-server.sh
@@ -46,7 +46,7 @@ test_expect_success 'setup' '
   touch secondrootfile &&
   git add secondrootfile &&
   git commit -m "second root") &&
-  git pull secondroot master &&
+  git pull --merge secondroot master &&
   git clone -q --bare "$WORKDIR/.git" "$SERVERDIR" >/dev/null 2>&1 &&
   GIT_DIR="$SERVERDIR" git config --bool gitcvs.enabled true &&
   GIT_DIR="$SERVERDIR" git config gitcvs.logfile "$SERVERDIR/gitcvs.log" &&
diff --git a/t/t9500-gitweb-standalone-no-errors.sh b/t/t9500-gitweb-standalone-no-errors.sh
index 6fca193..787c6cc 100755
--- a/t/t9500-gitweb-standalone-no-errors.sh
+++ b/t/t9500-gitweb-standalone-no-errors.sh
@@ -328,7 +328,7 @@ test_expect_success \
 	 git add b &&
 	 git commit -a -m "On branch" &&
 	 git checkout master &&
-	 git pull . b &&
+	 git pull --merge . b &&
 	 git tag merge_commit'
 
 test_expect_success \
-- 
1.8.3.1-794-ga13ccd6