diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index b4314568f..3b87f1a1b 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -466,6 +466,30 @@ sure that the current HEAD is "B", and call
 $ git rebase -i -p --onto Q O
 -----------------------------
 
+Reordering and editing commits usually creates untested intermediate
+steps.  You may want to check that your history editing did not break
+anything by running a test, or at least recompiling at intermediate
+points in history by using the "exec" command (shortcut "x").  You may
+do so by creating a todo list like this one:
+
+-------------------------------------------
+pick deadbee Implement feature XXX
+fixup f1a5c00 Fix to feature XXX
+exec make
+pick c0ffeee The oneline of the next commit
+edit deadbab The oneline of the commit after
+exec cd subdir; make test
+...
+-------------------------------------------
+
+The interactive rebase will stop when a command fails (i.e. exits with
+non-0 status) to give you an opportunity to fix the problem. You can
+continue with `git rebase --continue`.
+
+The "exec" command launches the command in a shell (the one specified
+in `$SHELL`, or the default shell if `$SHELL` is not set), so you can
+use shell features (like "cd", ">", ";" ...). The command is run from
+the root of the working tree.
 
 SPLITTING COMMITS
 -----------------
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index b94c2a038..3419247d0 100755
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -537,6 +537,34 @@ do_next () {
 		esac
 		record_in_rewritten $sha1
 		;;
+	x|"exec")
+		read -r command rest < "$TODO"
+		mark_action_done
+		printf 'Executing: %s\n' "$rest"
+		# "exec" command doesn't take a sha1 in the todo-list.
+		# => can't just use $sha1 here.
+		git rev-parse --verify HEAD > "$DOTEST"/stopped-sha
+		${SHELL:-@SHELL_PATH@} -c "$rest" # Actual execution
+		status=$?
+		if test "$status" -ne 0
+		then
+			warn "Execution failed: $rest"
+			warn "You can fix the problem, and then run"
+			warn
+			warn "	git rebase --continue"
+			warn
+			exit "$status"
+		fi
+		# Run in subshell because require_clean_work_tree can die.
+		if ! (require_clean_work_tree)
+		then
+			warn "Commit or stash your changes, and then run"
+			warn
+			warn "	git rebase --continue"
+			warn
+			exit 1
+		fi
+		;;
 	*)
 		warn "Unknown command: $command $sha1 $rest"
 		if git rev-parse --verify -q "$sha1" >/dev/null
@@ -591,22 +619,30 @@ do_rest () {
 # skip picking commits whose parents are unchanged
 skip_unnecessary_picks () {
 	fd=3
-	while read -r command sha1 rest
+	while read -r command rest
 	do
 		# fd=3 means we skip the command
-		case "$fd,$command,$(git rev-parse --verify --quiet $sha1^)" in
-		3,pick,"$ONTO"*|3,p,"$ONTO"*)
+		case "$fd,$command" in
+		3,pick|3,p)
 			# pick a commit whose parent is current $ONTO -> skip
-			ONTO=$sha1
+			sha1=$(printf '%s' "$rest" | cut -d ' ' -f 1)
+			case "$(git rev-parse --verify --quiet "$sha1"^)" in
+			"$ONTO"*)
+				ONTO=$sha1
+				;;
+			*)
+				fd=1
+				;;
+			esac
 			;;
-		3,#*|3,,*)
+		3,#*|3,)
 			# copy comments
 			;;
 		*)
 			fd=1
 			;;
 		esac
-		printf '%s\n' "$command${sha1:+ }$sha1${rest:+ }$rest" >&$fd
+		printf '%s\n' "$command${rest:+ }$rest" >&$fd
 	done <"$TODO" >"$TODO.new" 3>>"$DONE" &&
 	mv -f "$TODO".new "$TODO" &&
 	case "$(peek_next_command)" in
@@ -957,6 +993,7 @@ first and then run 'git rebase --continue' again."
 #  e, edit = use commit, but stop for amending
 #  s, squash = use commit, but meld into previous commit
 #  f, fixup = like "squash", but discard this commit's log message
+#  x <cmd>, exec <cmd> = Run a shell command <cmd>, and stop if it fails
 #
 # If you remove a line here THAT COMMIT WILL BE LOST.
 # However, if you remove everything, the rebase will be aborted.
diff --git a/t/README b/t/README
index 0d1183c3e..410499a09 100644
--- a/t/README
+++ b/t/README
@@ -467,6 +467,13 @@ library for your script to use.
    <expected> file.  This behaves like "cmp" but produces more
    helpful output when the test is run with "-v" option.
 
+ - test_path_is_file <file> [<diagnosis>]
+   test_path_is_dir <dir> [<diagnosis>]
+   test_path_is_missing <path> [<diagnosis>]
+
+   Check whether a file/directory exists or doesn't. <diagnosis> will
+   be displayed if the test fails.
+
  - test_when_finished <script>
 
    Prepend <script> to a list of commands to run to clean up
diff --git a/t/lib-rebase.sh b/t/lib-rebase.sh
index 6aefe2759..6ccf79709 100644
--- a/t/lib-rebase.sh
+++ b/t/lib-rebase.sh
@@ -47,6 +47,8 @@ for line in $FAKE_LINES; do
 	case $line in
 	squash|fixup|edit|reword)
 		action="$line";;
+	exec*)
+		echo "$line" | sed 's/_/ /g' >> "$1";;
 	"#")
 		echo '# comment' >> "$1";;
 	">")
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 3af3f603f..af3b663ae 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -64,6 +64,67 @@ test_expect_success 'setup' '
 	done
 '
 
+# "exec" commands are ran with the user shell by default, but this may
+# be non-POSIX. For example, if SHELL=zsh then ">file" doesn't work
+# to create a file. Unseting SHELL avoids such non-portable behavior
+# in tests.
+SHELL=
+
+test_expect_success 'rebase -i with the exec command' '
+	git checkout master &&
+	(
+	FAKE_LINES="1 exec_>touch-one
+		2 exec_>touch-two exec_false exec_>touch-three
+		3 4 exec_>\"touch-file__name_with_spaces\";_>touch-after-semicolon 5" &&
+	export FAKE_LINES &&
+	test_must_fail git rebase -i A
+	) &&
+	test_path_is_file touch-one &&
+	test_path_is_file touch-two &&
+	test_path_is_missing touch-three " (should have stopped before)" &&
+	test $(git rev-parse C) = $(git rev-parse HEAD) || {
+		echo "Stopped at wrong revision:"
+		echo "($(git describe --tags HEAD) instead of C)"
+		false
+	} &&
+	git rebase --continue &&
+	test_path_is_file touch-three &&
+	test_path_is_file "touch-file  name with spaces" &&
+	test_path_is_file touch-after-semicolon &&
+	test $(git rev-parse master) = $(git rev-parse HEAD) || {
+		echo "Stopped at wrong revision:"
+		echo "($(git describe --tags HEAD) instead of master)"
+		false
+	} &&
+	rm -f touch-*
+'
+
+test_expect_success 'rebase -i with the exec command runs from tree root' '
+	git checkout master &&
+	mkdir subdir && cd subdir &&
+	FAKE_LINES="1 exec_>touch-subdir" \
+		git rebase -i HEAD^ &&
+	cd .. &&
+	test_path_is_file touch-subdir &&
+	rm -fr subdir
+'
+
+test_expect_success 'rebase -i with the exec command checks tree cleanness' '
+	git checkout master &&
+	(
+	FAKE_LINES="exec_echo_foo_>file1 1" &&
+	export FAKE_LINES &&
+	test_must_fail git rebase -i HEAD^
+	) &&
+	test $(git rev-parse master^) = $(git rev-parse HEAD) || {
+		echo "Stopped at wrong revision:"
+		echo "($(git describe --tags HEAD) instead of master^)"
+		false
+	} &&
+	git reset --hard &&
+	git rebase --continue
+'
+
 test_expect_success 'no changes are a nop' '
 	git checkout branch2 &&
 	git rebase -i F &&
@@ -143,7 +204,7 @@ test_expect_success 'abort' '
 	git rebase --abort &&
 	test $(git rev-parse new-branch1) = $(git rev-parse HEAD) &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/branch1" &&
-	! test -d .git/rebase-merge
+	test_path_is_missing .git/rebase-merge
 '
 
 test_expect_success 'abort with error when new base cannot be checked out' '
@@ -153,7 +214,7 @@ test_expect_success 'abort with error when new base cannot be checked out' '
 	grep "The following untracked working tree files would be overwritten by checkout:" \
 		output &&
 	grep "file1" output &&
-	! test -d .git/rebase-merge &&
+	test_path_is_missing .git/rebase-merge &&
 	git reset --hard HEAD^
 '
 
diff --git a/t/t3407-rebase-abort.sh b/t/t3407-rebase-abort.sh
index 2999e7893..fbb3f2e0d 100755
--- a/t/t3407-rebase-abort.sh
+++ b/t/t3407-rebase-abort.sh
@@ -38,7 +38,7 @@ testrebase() {
 		# Clean up the state from the previous one
 		git reset --hard pre-rebase &&
 		test_must_fail git rebase$type master &&
-		test -d "$dotest" &&
+		test_path_is_dir "$dotest" &&
 		git rebase --abort &&
 		test $(git rev-parse to-rebase) = $(git rev-parse pre-rebase) &&
 		test ! -d "$dotest"
@@ -49,7 +49,7 @@ testrebase() {
 		# Clean up the state from the previous one
 		git reset --hard pre-rebase &&
 		test_must_fail git rebase$type master &&
-		test -d "$dotest" &&
+		test_path_is_dir "$dotest" &&
 		test_must_fail git rebase --skip &&
 		test $(git rev-parse HEAD) = $(git rev-parse master) &&
 		git rebase --abort &&
@@ -62,7 +62,7 @@ testrebase() {
 		# Clean up the state from the previous one
 		git reset --hard pre-rebase &&
 		test_must_fail git rebase$type master &&
-		test -d "$dotest" &&
+		test_path_is_dir "$dotest" &&
 		echo c > a &&
 		echo d >> a &&
 		git add a &&
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 29fd7209c..3a3d4c472 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -545,6 +545,38 @@ test_external_without_stderr () {
 	fi
 }
 
+# debugging-friendly alternatives to "test [-f|-d|-e]"
+# The commands test the existence or non-existence of $1. $2 can be
+# given to provide a more precise diagnosis.
+test_path_is_file () {
+	if ! [ -f "$1" ]
+	then
+		echo "File $1 doesn't exist. $*"
+		false
+	fi
+}
+
+test_path_is_dir () {
+	if ! [ -d "$1" ]
+	then
+		echo "Directory $1 doesn't exist. $*"
+		false
+	fi
+}
+
+test_path_is_missing () {
+	if [ -e "$1" ]
+	then
+		echo "Path exists:"
+		ls -ld "$1"
+		if [ $# -ge 1 ]; then
+			echo "$*"
+		fi
+		false
+	fi
+}
+
+
 # This is not among top-level (test_expect_success | test_expect_failure)
 # but is a prefix that can be used in the test script, like:
 #