Merge branch 'jk/pull-rebase-using-fork-point'

* jk/pull-rebase-using-fork-point:
  rebase: use reflog to find common base with upstream
  pull: use merge-base --fork-point when appropriate

Documentation/git-rebase.txt

@@ -324,6 +324,16 @@ fresh commits so it can be remerged successfully without needing to "revert
 the reversion" (see the
 link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details).
 
+--fork-point::
+--no-fork-point::
+	Use 'git merge-base --fork-point' to find a better common ancestor
+	between `upstream` and `branch` when calculating which commits have
+	have been introduced by `branch` (see linkgit:git-merge-base[1]).
++
+If no non-option arguments are given on the command line, then the default is
+`--fork-point @{u}` otherwise the `upstream` argument is interpreted literally
+unless the `--fork-point` option is specified.
+
 --ignore-whitespace::
 --whitespace=<option>::
 	These flag are passed to the 'git apply' program

git-pull.sh

@@ -229,15 +229,7 @@ test true = "$rebase" && {
 	test -n "$curr_branch" &&
 	. git-parse-remote &&
 	remoteref="$(get_remote_merge_branch "$@" 2>/dev/null)" &&
-	oldremoteref="$(git rev-parse -q --verify "$remoteref")" &&
-	for reflog in $(git rev-list -g $remoteref 2>/dev/null)
-	do
-		if test "$reflog" = "$(git merge-base $reflog $curr_branch)"
-		then
-			oldremoteref="$reflog"
-			break
-		fi
-	done
+	oldremoteref=$(git merge-base --fork-point "$remoteref" $curr_branch)
 }
 orig_head=$(git rev-parse -q --verify HEAD)
 git fetch $verbosity $progress $dry_run $recurse_submodules --update-head-ok "$@" || exit 1

git-rebase.sh

@@ -14,6 +14,7 @@ git-rebase --continue | --abort | --skip | --edit-todo
 v,verbose!         display a diffstat of what changed upstream
 q,quiet!           be quiet. implies --no-stat
 autostash!         automatically stash/stash pop before and after
+fork-point         use 'merge-base --fork-point' to refine upstream
 onto=!             rebase onto given branch instead of upstream
 p,preserve-merges! try to recreate merges instead of ignoring them
 s,strategy=!       use the given merge strategy
@@ -66,6 +67,7 @@ verbose=
 diffstat=
 test "$(git config --bool rebase.stat)" = true && diffstat=t
 autostash="$(git config --bool rebase.autostash || echo false)"
+fork_point=auto
 git_am_opt=
 rebase_root=
 force_rebase=
@@ -260,6 +262,12 @@ do
 	--no-autosquash)
 		autosquash=
 		;;
+	--fork-point)
+		fork_point=t
+		;;
+	--no-fork-point)
+		fork_point=
+		;;
 	-M|-m)
 		do_merge=t
 		;;
@@ -437,6 +445,8 @@ then
 			error_on_missing_default_upstream "rebase" "rebase" \
 				"against" "git rebase <branch>"
 		fi
+
+		test "$fork_point" = auto && fork_point=t
 		;;
 	*)	upstream_name="$1"
 		shift
@@ -522,6 +532,15 @@ case "$#" in
 	;;
 esac
 
+if test "$fork_point" = t
+then
+	new_upstream=$(git merge-base --fork-point "$upstream_name" "$switch_to")
+	if test -n "$new_upstream"
+	then
+		upstream=$new_upstream
+	fi
+fi
+
 if test "$autostash" = true && ! (require_clean_work_tree) 2>/dev/null
 then
 	stash_sha1=$(git stash create "autostash") ||

t/t3400-rebase.sh

@@ -134,12 +134,14 @@ test_expect_success 'fail when upstream arg is missing and not configured' '
 	test_must_fail git rebase
 '
 
-test_expect_success 'default to @{upstream} when upstream arg is missing' '
+test_expect_success 'default to common base in @{upstream}s reflog if no upstream arg' '
 	git checkout -b default topic &&
 	git config branch.default.remote . &&
 	git config branch.default.merge refs/heads/master &&
 	git rebase &&
-	test "$(git rev-parse default~1)" = "$(git rev-parse master)"
+	git rev-parse --verify master >expect &&
+	git rev-parse default~1 >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'rebase -q is quiet' '