stash: simplify defaulting to "save" and reject unknown options

With the earlier DWIM patches, certain combination of options defaulted
to the "save" command correctly while certain equally valid combination
did not.  For example, "git stash -k" were Ok but "git stash -q -k" did
not work.

This makes the logic of defaulting to "save" much simpler. If there are no
non-flag arguments, it is clear that there is no command word, and we
default to "save" subcommand.  This rule prevents "git stash -q apply"
from quietly creating a stash with "apply" as the message.

This also teaches "git stash save" to reject an unknown option.  This is
to keep a mistyped "git stash save --quite" from creating a stash with a
message "--quite", and this safety is more important with the new logic
to default to "save" with any option-looking argument without an explicit
comand word.

[jc: this is based on Matthieu's 3-patch series, and a follow-up
discussion, and he and Peff take all the credit; if I have introduced bugs
while reworking, they are mine.]

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-stash.txt

@@ -14,7 +14,6 @@ SYNOPSIS
 'git stash' ( pop | apply ) [--index] [-q|--quiet] [<stash>]
 'git stash' branch <branchname> [<stash>]
 'git stash' [save [--patch] [-k|--[no-]keep-index] [-q|--quiet] [<message>]]
-'git stash' [-p|--patch|-k|--keep-index]
 'git stash' clear
 'git stash' create
 
@@ -46,9 +45,11 @@ OPTIONS
 save [--patch] [--[no-]keep-index] [-q|--quiet] [<message>]::
 
 	Save your local modifications to a new 'stash', and run `git reset
-	--hard` to revert them.  This is the default action when no
-	subcommand is given. The <message> part is optional and gives
-	the description along with the stashed state.
+	--hard` to revert them.  The <message> part is optional and gives
+	the description along with the stashed state.  For quickly making
+	a snapshot, you can omit _both_ "save" and <message>, but giving
+	only <message> does not trigger this action to prevent a misspelled
+	subcommand from making an unwanted stash.
 +
 If the `--keep-index` option is used, all changes already added to the
 index are left intact.

git-stash.sh

@@ -8,7 +8,6 @@ USAGE="list [<options>]
    or: $dashless ( pop | apply ) [--index] [-q|--quiet] [<stash>]
    or: $dashless branch <branchname> [<stash>]
    or: $dashless [save [-k|--keep-index] [-q|--quiet] [<message>]]
-   or: $dashless [-k|--keep-index]
    or: $dashless clear"
 
 SUBDIRECTORY_OK=Yes
@@ -146,6 +145,14 @@ save_stash () {
 		-q|--quiet)
 			GIT_QUIET=t
 			;;
+		--)
+			shift
+			break
+			;;
+		-*)
+			echo "error: unknown option for 'stash save': $1"
+			usage
+			;;
 		*)
 			break
 			;;
@@ -355,6 +362,18 @@ apply_to_branch () {
 	drop_stash $stash
 }
 
+# The default command is "save" if nothing but options are given
+seen_non_option=
+for opt
+do
+	case "$opt" in
+	-*) ;;
+	*) seen_non_option=t; break ;;
+	esac
+done
+
+test -n "$seen_non_option" || set "save" "$@"
+
 # Main command set
 case "$1" in
 list)
@@ -406,9 +425,9 @@ branch)
 	apply_to_branch "$@"
 	;;
 *)
-	case $#,"$1","$2" in
-	0,,|1,-k,|1,--keep-index,|1,-p,|1,--patch,|2,-p,--no-keep-index|2,--patch,--no-keep-index)
-		save_stash "$@" &&
+	case $# in
+	0)
+		save_stash &&
 		say '(To restore them type "git stash apply")'
 		;;
 	*)

t/t3903-stash.sh

@@ -208,4 +208,15 @@ test_expect_success 'stash -k' '
 	test bar,bar4 = $(cat file),$(cat file2)
 '
 
+test_expect_success 'stash --invalid-option' '
+	echo bar5 > file &&
+	echo bar6 > file2 &&
+	git add file2 &&
+	test_must_fail git stash --invalid-option &&
+	test_must_fail git stash save --invalid-option &&
+	test bar5,bar6 = $(cat file),$(cat file2) &&
+	git stash -- -message-starting-with-dash &&
+	test bar,bar2 = $(cat file),$(cat file2)
+'
+
 test_done