wt-status.c: handle worktree renames

Before 425a28e0a4 (diff-lib: allow ita entries treated as "not yet exist
in index" - 2016-10-24) there are never "new files" in the index, which
essentially disables rename detection because we only detect renames
when a new file appears in a diff pair.

After that commit, an i-t-a entry can appear as a new file in "git
diff-files". But the diff callback function in wt-status.c does not
handle this case and produces incorrect status output.

PS. The reader may notice that this patch adds a new xstrdup() but not
a free(). Yes we leak memory (the same for head_path). But wt_status
so far has been short lived, this leak should not matter in
practice.

Noticed-by: Alex Vandiver <alexmv@dropbox.com>
Helped-by: Igor Djordjevic <igor.d.djordjevic@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-status.txt

@@ -125,14 +125,15 @@ the status.relativePaths config option below.
 Short Format
 ~~~~~~~~~~~~
 
-In the short-format, the status of each path is shown as
+In the short-format, the status of each path is shown as one of these
+forms
 
-	XY PATH1 -> PATH2
+	XY PATH
+	XY ORIG_PATH -> PATH
 
-where `PATH1` is the path in the `HEAD`, and the " `-> PATH2`" part is
-shown only when `PATH1` corresponds to a different path in the
-index/worktree (i.e. the file is renamed). The `XY` is a two-letter
-status code.
+where `ORIG_PATH` is where the renamed/copied contents came
+from. `ORIG_PATH` is only shown when the entry is renamed or
+copied. The `XY` is a two-letter status code.
 
 The fields (including the `->`) are separated from each other by a
 single space. If a filename contains whitespace or other nonprintable
@@ -168,6 +169,8 @@ in which case `XY` are `!!`.
     [MARC]           index and work tree matches
     [ MARC]     M    work tree changed since index
     [ MARC]     D    deleted in work tree
+    [ D]        R    renamed in work tree
+    [ D]        C    copied in work tree
     -------------------------------------------------
     D           D    unmerged, both deleted
     A           U    unmerged, added by us
@@ -285,13 +288,13 @@ Renamed or copied entries have the following format:
 		of similarity between the source and target of the
 		move or copy). For example "R100" or "C75".
     <path>      The pathname.  In a renamed/copied entry, this
-		is the path in the index and in the working tree.
+		is the target path.
     <sep>       When the `-z` option is used, the 2 pathnames are separated
 		with a NUL (ASCII 0x00) byte; otherwise, a tab (ASCII 0x09)
 		byte separates them.
-    <origPath>  The pathname in the commit at HEAD.  This is only
-		present in a renamed/copied entry, and tells
-		where the renamed/copied contents came from.
+    <origPath>  The pathname in the commit at HEAD or in the index.
+		This is only present in a renamed/copied entry, and
+		tells where the renamed/copied contents came from.
     --------------------------------------------------------
 
 Unmerged entries have the following format; the first character is

t/t2203-add-intent.sh

@@ -162,5 +162,65 @@ test_expect_success 'commit: ita entries ignored in empty commit check' '
 	)
 '
 
+test_expect_success 'rename detection finds the right names' '
+	git init rename-detection &&
+	(
+		cd rename-detection &&
+		echo contents >first &&
+		git add first &&
+		git commit -m first &&
+		mv first third &&
+		git add -N third &&
+
+		git status | grep -v "^?" >actual.1 &&
+		test_i18ngrep "renamed: *first -> third" actual.1 &&
+
+		git status --porcelain | grep -v "^?" >actual.2 &&
+		cat >expected.2 <<-\EOF &&
+		 R first -> third
+		EOF
+		test_cmp expected.2 actual.2 &&
+
+		hash=12f00e90b6ef79117ce6e650416b8cf517099b78 &&
+		git status --porcelain=v2 | grep -v "^?" >actual.3 &&
+		cat >expected.3 <<-EOF &&
+		2 .R N... 100644 100644 100644 $hash $hash R100 third	first
+		EOF
+		test_cmp expected.3 actual.3
+	)
+'
+
+test_expect_success 'double rename detection in status' '
+	git init rename-detection-2 &&
+	(
+		cd rename-detection-2 &&
+		echo contents >first &&
+		git add first &&
+		git commit -m first &&
+		git mv first second &&
+		mv second third &&
+		git add -N third &&
+
+		git status | grep -v "^?" >actual.1 &&
+		test_i18ngrep "renamed: *first -> second" actual.1 &&
+		test_i18ngrep "renamed: *second -> third" actual.1 &&
+
+		git status --porcelain | grep -v "^?" >actual.2 &&
+		cat >expected.2 <<-\EOF &&
+		R  first -> second
+		 R second -> third
+		EOF
+		test_cmp expected.2 actual.2 &&
+
+		hash=12f00e90b6ef79117ce6e650416b8cf517099b78 &&
+		git status --porcelain=v2 | grep -v "^?" >actual.3 &&
+		cat >expected.3 <<-EOF &&
+		2 R. N... 100644 100644 100644 $hash $hash R100 second	first
+		2 .R N... 100644 100644 100644 $hash $hash R100 third	second
+		EOF
+		test_cmp expected.3 actual.3
+	)
+'
+
 test_done
 

wt-status.c

@@ -361,8 +361,6 @@ static void wt_longstatus_print_change_data(struct wt_status *s,
 	switch (change_type) {
 	case WT_STATUS_UPDATED:
 		status = d->index_status;
-		if (d->rename_source)
-			one_name = d->rename_source;
 		break;
 	case WT_STATUS_CHANGED:
 		if (d->new_submodule_commits || d->dirty_submodule) {
@@ -383,6 +381,14 @@ static void wt_longstatus_print_change_data(struct wt_status *s,
 		    change_type);
 	}
 
+	/*
+	 * Only pick up the rename it's relevant. If the rename is for
+	 * the changed section and we're printing the updated section,
+	 * ignore it.
+	 */
+	if (d->rename_status == status)
+		one_name = d->rename_source;
+
 	one = quote_path(one_name, s->prefix, &onebuf);
 	two = quote_path(two_name, s->prefix, &twobuf);
 
@@ -434,7 +440,7 @@ static void wt_status_collect_changed_cb(struct diff_queue_struct *q,
 		struct wt_status_change_data *d;
 
 		p = q->queue[i];
-		it = string_list_insert(&s->change, p->one->path);
+		it = string_list_insert(&s->change, p->two->path);
 		d = it->util;
 		if (!d) {
 			d = xcalloc(1, sizeof(*d));
@@ -461,6 +467,14 @@ static void wt_status_collect_changed_cb(struct diff_queue_struct *q,
 			/* mode_worktree is zero for a delete. */
 			break;
 
+		case DIFF_STATUS_COPIED:
+		case DIFF_STATUS_RENAMED:
+			if (d->rename_status)
+				die("BUG: multiple renames on the same target? how?");
+			d->rename_source = xstrdup(p->one->path);
+			d->rename_score = p->score * 100 / MAX_SCORE;
+			d->rename_status = p->status;
+			/* fallthru */
 		case DIFF_STATUS_MODIFIED:
 		case DIFF_STATUS_TYPE_CHANGED:
 		case DIFF_STATUS_UNMERGED:
@@ -532,6 +546,8 @@ static void wt_status_collect_updated_cb(struct diff_queue_struct *q,
 
 		case DIFF_STATUS_COPIED:
 		case DIFF_STATUS_RENAMED:
+			if (d->rename_status)
+				die("BUG: multiple renames on the same target? how?");
 			d->rename_source = xstrdup(p->one->path);
 			d->rename_score = p->score * 100 / MAX_SCORE;
 			d->rename_status = p->status;