CodingGuidelines: allow declaring variables in for loops

Since 44ba10d (revision: use C99 declaration of variable in for()
loop, 2021-11-14) released with v2.35.0 we've had a variable declared
with in a for loop.

Since then we've had inadvertent follow-ups to that with at least
cb26077 (merge-ort: store more specific conflict information,
2022-06-18) released with v2.38.0.

As November 2022 is within the window of this upcoming release,
let's update the guideline to allow this.  We can have the promised
"revisit" discussion while this patch cooks, and drop it if it turns
out that it is still premature, which is not expected to happen at
this moment.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

Documentation/CodingGuidelines

@@ -232,18 +232,12 @@ For C programs:
    . since early 2021 with 765dc168882, we have been using variadic
      macros, mostly for printf-like trace and debug macros.
 
-   These used to be forbidden, but we have not heard any breakage
-   report, and they are assumed to be safe.
+   . since late 2021 with 44ba10d6, we have had variables declared in
+     the for loop "for (int i = 0; i < 10; i++)".
 
  - Variables have to be declared at the beginning of the block, before
    the first statement (i.e. -Wdeclaration-after-statement).
 
- - Declaring a variable in the for loop "for (int i = 0; i < 10; i++)"
-   is still not allowed in this codebase.  We are in the process of
-   allowing it by waiting to see that 44ba10d6 (revision: use C99
-   declaration of variable in for() loop, 2021-11-14) does not get
-   complaints.  Let's revisit this around November 2022.
-
  - NULL pointers shall be written as NULL, not as 0.
 
  - When declaring pointers, the star sides with the variable

revision.c

@@ -47,13 +47,6 @@ static inline int want_ancestry(const struct rev_info *revs);
 void show_object_with_name(FILE *out, struct object *obj, const char *name)
 {
 	fprintf(out, "%s ", oid_to_hex(&obj->oid));
-	/*
-	 * This "for (const char *p = ..." is made as a first step towards
-	 * making use of such declarations elsewhere in our codebase.  If
-	 * it causes compilation problems on your platform, please report
-	 * it to the Git mailing list at [email protected]. In the meantime,
-	 * adding -std=gnu99 to CFLAGS may help if you are with older GCC.
-	 */
 	for (const char *p = name; *p && *p != '\n'; p++)
 		fputc(*p, out);
 	fputc('\n', out);