[PATCHv2] fix broken list iteration in clear_child_for_cleanup

We iterate through the list of children to cleanup, but do not keep
our "last" pointer up to date. As a result, we may end up cutting off
part of the list instead of removing a single element.

Iterate through children_to_clean using 'next' fields but with an
extra level of indirection. This allows us to update the chain when
we remove a child and saves us managing several variables around
the loop mechanism.

Signed-off-by: David Gould <redacted>
Acked-by: Jeff King <redacted>
---
PATCHv2 updates PATCH only in the commit message: Peff suggested
both a helpful subject and a more-informative introduction.

 run-command.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/run-command.c b/run-command.c
index f9922b9..c42d63b 100644
--- a/run-command.c
+++ b/run-command.c

@@ -53,13 +53,13 @@ static void mark_child_for_cleanup(pid_t pid)
 
 static void clear_child_for_cleanup(pid_t pid)
 {
-	struct child_to_clean **last, *p;
+	struct child_to_clean **pp;
 
-	last = &children_to_clean;
-	for (p = children_to_clean; p; p = p->next) {
-		if (p->pid == pid) {
-			*last = p->next;
-			free(p);
+	for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
+		if ((*pp)->pid == pid) {
+			struct child_to_clean *clean_me = *pp;
+			*pp = clean_me->next;
+			free(clean_me);
 			return;
 		}
 	}

-- 
1.7.9.5