[PATCHv2 3/5] revision.c: stricter parsing of '--early-output'

["SZEDER Gábor" <szeder.dev@gmail.com>]

The parsing of '--early-output' with or without its optional integer
argument allowed bogus options like '--early-output-foobarbaz' to slip
through and be ignored.

Fix it by parsing '--early-output' in the same way as other options
with an optional argument are parsed.  Furthermore, use strtoul_ui()
to parse the optional integer argument and to refuse negative numbers.

While at it, use skip_prefix() instead of starts_with() and magic
numbers.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 revision.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/revision.c b/revision.c
index 2f37e1e3a..68531ff5d 100644
--- a/revision.c
+++ b/revision.c
@@ -1785,16 +1785,13 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--author-date-order")) {
 		revs->sort_order = REV_SORT_BY_AUTHOR_DATE;
 		revs->topo_order = 1;
-	} else if (starts_with(arg, "--early-output")) {
-		int count = 100;
-		switch (arg[14]) {
-		case '=':
-			count = atoi(arg+15);
-			/* Fallthrough */
-		case 0:
-			revs->topo_order = 1;
-		       revs->early_output = count;
-		}
+	} else if (!strcmp(arg, "--early-output")) {
+		revs->early_output = 100;
+		revs->topo_order = 1;
+	} else if (skip_prefix(arg, "--early-output=", &optarg)) {
+		if (strtoul_ui(optarg, 10, &revs->early_output) < 0)
+			die("'%s': not a non-negative integer", optarg);
+		revs->topo_order = 1;
 	} else if (!strcmp(arg, "--parents")) {
 		revs->rewrite_parents = 1;
 		revs->print_parents = 1;
-- 
2.13.0.420.g54001f015