[PATCH v2 08/22] run-command.c: use C99 "for (TYPE VAR = ..." syntax where useful

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Refactor code in run-command.c where the "i" iteration variable is
being compared to an unsigned type, or where it's being shadowed.

In a subsequent commit the type of the "n" variable will be changed,
this also helps to avoid some of the warnings we've had under
"DEVOPTS=extra-all" since 8d133a4653a (strvec: use size_t to store nr
and alloc, 2021-09-11).

Per the thread ending at [1] we already have this C99 syntax in the
v2.38.0 release, per 6563706568b (CodingGuidelines: give deadline for
"for (int i = 0; ...", 2022-03-30) we should re-visit the wider use of
this syntax for November 2022, meaning within the window of v2.39.0.

As of writing it's earlier than that deadline and per [1] we want to
"avoid open[ing] the floodgate and deliberately add more [this C99
syntax]". But in this case the use of the syntax solves a real problem
of conflating types, which we'd otherwise need to avoid by using
differently named iteration variables (and the associated larger
refactoring).

1. https://lore.kernel.org/git/xmqqy1wgwkbj.fsf@gitster.g/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 run-command.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/run-command.c b/run-command.c
index bd45828fe2c..7b27e4de78d 100644
--- a/run-command.c
+++ b/run-command.c
@@ -443,7 +443,6 @@ static char **prep_childenv(const char *const *deltaenv)
 	struct string_list env = STRING_LIST_INIT_DUP;
 	struct strbuf key = STRBUF_INIT;
 	const char *const *p;
-	int i;
 
 	/* Construct a sorted string list consisting of the current environ */
 	for (p = (const char *const *) environ; p && *p; p++) {
@@ -476,7 +475,7 @@ static char **prep_childenv(const char *const *deltaenv)
 
 	/* Create an array of 'char *' to be used as the childenv */
 	ALLOC_ARRAY(childenv, env.nr + 1);
-	for (i = 0; i < env.nr; i++)
+	for (size_t i = 0; i < env.nr; i++)
 		childenv[i] = env.items[i].util;
 	childenv[env.nr] = NULL;
 
@@ -581,7 +580,6 @@ static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 {
 	struct string_list envs = STRING_LIST_INIT_DUP;
 	const char *const *e;
-	int i;
 	int printed_unset = 0;
 
 	/* Last one wins, see run-command.c:prep_childenv() for context */
@@ -599,7 +597,7 @@ static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 	}
 
 	/* "unset X Y...;" */
-	for (i = 0; i < envs.nr; i++) {
+	for (size_t i = 0; i < envs.nr; i++) {
 		const char *var = envs.items[i].string;
 		const char *val = envs.items[i].util;
 
@@ -616,7 +614,7 @@ static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 		strbuf_addch(dst, ';');
 
 	/* ... followed by "A=B C=D ..." */
-	for (i = 0; i < envs.nr; i++) {
+	for (size_t i = 0; i < envs.nr; i++) {
 		const char *var = envs.items[i].string;
 		const char *val = envs.items[i].util;
 		const char *oldval;
@@ -1789,7 +1787,7 @@ void run_processes_parallel(int n,
 			    task_finished_fn task_finished,
 			    void *pp_cb)
 {
-	int i, code;
+	int code;
 	int output_timeout = 100;
 	int spawn_cap = 4;
 	int ungroup = run_processes_parallel_ungroup;
@@ -1801,7 +1799,7 @@ void run_processes_parallel(int n,
 	pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb,
 		ungroup);
 	while (1) {
-		for (i = 0;
+		for (int i = 0;
 		    i < spawn_cap && !pp.shutdown &&
 		    pp.nr_processes < pp.max_processes;
 		    i++) {
-- 
2.38.0.971.ge79ff6d20e7