run-command: factor out child_process_clear()

Avoid duplication by moving the code to release allocated memory for
arguments and environment to its own function, child_process_clear().
Export it to provide a counterpart to child_process_init().

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-run-command.txt

diff --git a/Documentation/technical/api-run-command.txt b/Documentation/technical/api-run-command.txt
index a9fdb45..8bf3e37 100644
--- a/Documentation/technical/api-run-command.txt
+++ b/Documentation/technical/api-run-command.txt
@@ -46,6 +46,13 @@
 	The argument dir corresponds the member .dir. The argument env
 	corresponds to the member .env.
 
+`child_process_clear`::
+
+	Release the memory associated with the struct child_process.
+	Most users of the run-command API don't need to call this
+	function explicitly because `start_command` invokes it on
+	failure and `finish_command` calls it automatically already.
+
 The functions above do the following:
 
 . If a system call failed, errno is set and -1 is returned. A diagnostic

run-command.c

diff --git a/run-command.c b/run-command.c
index aad03ab..fc391fb 100644
--- a/run-command.c
+++ b/run-command.c
@@ -11,6 +11,12 @@
 	argv_array_init(&child->env_array);
 }
 
+void child_process_clear(struct child_process *child)
+{
+	argv_array_clear(&child->args);
+	argv_array_clear(&child->env_array);
+}
+
 struct child_to_clean {
 	pid_t pid;
 	struct child_to_clean *next;
@@ -336,8 +342,7 @@
 fail_pipe:
 			error("cannot create %s pipe for %s: %s",
 				str, cmd->argv[0], strerror(failed_errno));
-			argv_array_clear(&cmd->args);
-			argv_array_clear(&cmd->env_array);
+			child_process_clear(cmd);
 			errno = failed_errno;
 			return -1;
 		}
@@ -523,8 +528,7 @@
 			close_pair(fderr);
 		else if (cmd->err)
 			close(cmd->err);
-		argv_array_clear(&cmd->args);
-		argv_array_clear(&cmd->env_array);
+		child_process_clear(cmd);
 		errno = failed_errno;
 		return -1;
 	}
@@ -550,8 +554,7 @@
 int finish_command(struct child_process *cmd)
 {
 	int ret = wait_or_whine(cmd->pid, cmd->argv[0]);
-	argv_array_clear(&cmd->args);
-	argv_array_clear(&cmd->env_array);
+	child_process_clear(cmd);
 	return ret;
 }
 

run-command.h

diff --git a/run-command.h b/run-command.h
index 263b966..c850a57 100644
--- a/run-command.h
+++ b/run-command.h
@@ -47,6 +47,7 @@
 
 #define CHILD_PROCESS_INIT { NULL, ARGV_ARRAY_INIT, ARGV_ARRAY_INIT }
 void child_process_init(struct child_process *);
+void child_process_clear(struct child_process *);
 
 int start_command(struct child_process *);
 int finish_command(struct child_process *);