reset: handle submodule with trailing slash

When using tab-completion, a directory path will often end with a
trailing slash which currently confuses "git reset" when dealing with
submodules.  Now that we have parse_pathspec we can easily handle this
by simply adding the PATHSPEC_STRIP_SUBMODULE_SLASH_CHEAP flag.

To do this, we need to move the read_cache() call before the
parse_pathspec() call.  All of the existing paths through cmd_reset()
that do not die early already call read_cache() at some point, so there
is no performance impact to doing this in the common case.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reset.c

@@ -143,7 +143,6 @@ static int read_from_tree(const struct pathspec *pathspec,
 	opt.output_format = DIFF_FORMAT_CALLBACK;
 	opt.format_callback = update_index_from_diff;
 
-	read_cache();
 	if (do_diff_cache(tree_sha1, &opt))
 		return 1;
 	diffcore_std(&opt);
@@ -169,7 +168,7 @@ static void set_reflog_message(struct strbuf *sb, const char *action,
 
 static void die_if_unmerged_cache(int reset_type)
 {
-	if (is_merge() || read_cache() < 0 || unmerged_cache())
+	if (is_merge() || unmerged_cache())
 		die(_("Cannot do a %s reset in the middle of a merge."),
 		    _(reset_type_names[reset_type]));
 
@@ -220,8 +219,13 @@ static void parse_args(struct pathspec *pathspec,
 		}
 	}
 	*rev_ret = rev;
+
+	if (read_cache() < 0)
+		die(_("index file corrupt"));
+
 	parse_pathspec(pathspec, 0,
 		       PATHSPEC_PREFER_FULL |
+		       PATHSPEC_STRIP_SUBMODULE_SLASH_CHEAP |
 		       (patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0),
 		       prefix, argv);
 }

t/t7400-submodule-basic.sh

@@ -481,7 +481,7 @@ test_expect_success 'do not add files from a submodule' '
 
 '
 
-test_expect_success 'gracefully add submodule with a trailing slash' '
+test_expect_success 'gracefully add/reset submodule with a trailing slash' '
 
 	git reset --hard &&
 	git commit -m "commit subproject" init &&
@@ -495,7 +495,9 @@ test_expect_success 'gracefully add submodule with a trailing slash' '
 	git add init/ &&
 	test_must_fail git diff --exit-code --cached init &&
 	test $commit = $(git ls-files --stage |
-		sed -n "s/^160000 \([^ ]*\).*/\1/p")
+		sed -n "s/^160000 \([^ ]*\).*/\1/p") &&
+	git reset init/ &&
+	git diff --exit-code --cached init
 
 '