[PATCH 1/2] stash: record positional index in 'struct stash_info'

get_stash_info() resolves revision arguments (such as 'stash@{0}'
or '2') and checks whether they refer to 'refs/stash', but it
does not allow callers to determine the 0-based positional
reflog index.

Record '.stash_idx' in 'struct stash_info'.  Populate it in
get_stash_info(), setting it to 0 when omitted (defaulting
to the latest stash), to 'n' when a valid positional index
'@{n}' is specified, or to -1 when the index specification
is invalid or non-positional (such as a time-based reference).

Subcommands that manipulate reflog entries by index can use
'.stash_idx' directly, instead of parsing the revision arguments
themselves.

Signed-off-by: Junio C Hamano <[email protected]>
---
 builtin/stash.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/builtin/stash.c b/builtin/stash.c
index c4809f299a..5041a9ba81 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -175,6 +175,7 @@ struct stash_info {
 	struct strbuf revision;
 	int is_stash_ref;
 	int has_u;
+	int stash_idx;
 };
 
 #define STASH_INFO_INIT { \
@@ -248,6 +249,7 @@ static int get_stash_info(struct stash_info *info, int argc, const char **argv)
 	char *expanded_ref;
 	const char *revision;
 	const char *commit = NULL;
+	const char *at;
 	struct object_id dummy;
 	struct strbuf symbolic = STRBUF_INIT;
 
@@ -300,6 +302,19 @@ static int get_stash_info(struct stash_info *info, int argc, const char **argv)
 	}
 
 	free(expanded_ref);
+
+	at = strstr(revision, "@{");
+	if (at) {
+		char *ep;
+		unsigned long u = strtoul(at + 2, &ep, 10);
+		if (ep > at + 2 && *ep == '}' && u < 100000000)
+			info->stash_idx = (int)u;
+		else
+			info->stash_idx = -1;
+	} else {
+		info->stash_idx = 0;
+	}
+
 	return !(ret == 0 || ret == 1);
 }
 
-- 
2.55.0-597-ge6126a35d6