refactor argv_array into generic code
The submodule code recently grew generic code to build a dynamic argv array. Many other parts of the code can reuse this, too, so let's make it generically available. There are two enhancements not found in the original code: 1. We now handle the NULL-termination invariant properly, even when no strings have been pushed (before, you could have an empty, NULL argv). This was not a problem for the submodule code, which always pushed at least one argument, but was not sufficiently safe for generic code. 2. There is a formatted variant of the "push" function. This is a convenience function which was not needed by the submodule code, but will make it easier to port other users to the new code. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Sep 13, 2011 at 17:57 UTC
c1189caeaf726e6c16c8bca7da8bf0b243da478d
5 files changed
+125
-35
Documentation/technical/api-argv-array.txt
new
+46
@@ -0,0 +1,46 @@
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+argv-array API
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+==============
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+
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+The argv-array API allows one to dynamically build and store
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+NULL-terminated lists. An argv-array maintains the invariant that the
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+`argv` member always points to a non-NULL array, and that the array is
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+always NULL-terminated at the element pointed to by `argv[argc]`. This
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+makes the result suitable for passing to functions expecting to receive
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+argv from main(), or the link:api-run-command.html[run-command API].
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+
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+The link:api-string-list.html[string-list API] is similar, but cannot be
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+used for these purposes; instead of storing a straight string pointer,
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+it contains an item structure with a `util` field that is not compatible
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+with the traditional argv interface.
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+
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+Each `argv_array` manages its own memory. Any strings pushed into the
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+array are duplicated, and all memory is freed by argv_array_clear().
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+
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+Data Structures
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+---------------
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+
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+`struct argv_array`::
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+
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+ A single array. This should be initialized by assignment from
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+ `ARGV_ARRAY_INIT`, or by calling `argv_array_init`. The `argv`
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+ member contains the actual array; the `argc` member contains the
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+ number of elements in the array, not including the terminating
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+ NULL.
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+
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+Functions
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+---------
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+
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+`argv_array_init`::
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+ Initialize an array. This is no different than assigning from
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+ `ARGV_ARRAY_INIT`.
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+
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+`argv_array_push`::
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+ Push a copy of a string onto the end of the array.
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+
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+`argv_array_pushf`::
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+ Format a string and push it onto the end of the array. This is a
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+ convenience wrapper combining `strbuf_addf` and `argv_array_push`.
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+
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+`argv_array_clear`::
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+ Free all memory associated with the array and return it to the
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+ initial, empty state.
Makefile
+2
@@ -497,6 +497,7 @@ VCSSVN_LIB=vcs-svn/lib.a
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LIB_H += advice.h
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LIB_H += archive.h
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+LIB_H += argv-array.h
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LIB_H += attr.h
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LIB_H += blob.h
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LIB_H += builtin.h
@@ -575,6 +576,7 @@ LIB_OBJS += alloc.o
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LIB_OBJS += archive.o
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LIB_OBJS += archive-tar.o
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LIB_OBJS += archive-zip.o
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+LIB_OBJS += argv-array.o
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LIB_OBJS += attr.o
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LIB_OBJS += base85.o
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LIB_OBJS += bisect.o
argv-array.c
new
+51
@@ -0,0 +1,51 @@
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+#include "cache.h"
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+#include "argv-array.h"
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+#include "strbuf.h"
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+
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+static const char *empty_argv_storage = NULL;
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+const char **empty_argv = &empty_argv_storage;
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+
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+void argv_array_init(struct argv_array *array)
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+{
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+ array->argv = empty_argv;
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+ array->argc = 0;
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+ array->alloc = 0;
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+}
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+
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+static void argv_array_push_nodup(struct argv_array *array, const char *value)
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+{
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+ if (array->argv == empty_argv)
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+ array->argv = NULL;
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+
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+ ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
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+ array->argv[array->argc++] = value;
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+ array->argv[array->argc] = NULL;
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+}
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+
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+void argv_array_push(struct argv_array *array, const char *value)
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+{
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+ argv_array_push_nodup(array, xstrdup(value));
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+}
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+
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+void argv_array_pushf(struct argv_array *array, const char *fmt, ...)
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+{
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+ va_list ap;
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+ struct strbuf v = STRBUF_INIT;
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+
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+ va_start(ap, fmt);
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+ strbuf_vaddf(&v, fmt, ap);
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+ va_end(ap);
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+
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+ argv_array_push_nodup(array, strbuf_detach(&v, NULL));
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+}
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+
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+void argv_array_clear(struct argv_array *array)
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+{
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+ if (array->argv != empty_argv) {
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+ int i;
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+ for (i = 0; i < array->argc; i++)
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+ free((char **)array->argv[i]);
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+ free(array->argv);
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+ }
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+ argv_array_init(array);
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+}
argv-array.h
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+20
@@ -0,0 +1,20 @@
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+#ifndef ARGV_ARRAY_H
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+#define ARGV_ARRAY_H
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+
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+extern const char **empty_argv;
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+
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+struct argv_array {
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+ const char **argv;
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+ int argc;
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+ int alloc;
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+};
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+
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+#define ARGV_ARRAY_INIT { empty_argv, 0, 0 }
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+
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+void argv_array_init(struct argv_array *);
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+void argv_array_push(struct argv_array *, const char *);
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+__attribute__((format (printf,2,3)))
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+void argv_array_pushf(struct argv_array *, const char *fmt, ...);
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+void argv_array_clear(struct argv_array *);
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+
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+#endif /* ARGV_ARRAY_H */
submodule.c
+6
-35
@@ -9,6 +9,7 @@
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#include "refs.h"
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#include "string-list.h"
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#include "sha1-array.h"
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+#include "argv-array.h"
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static struct string_list config_name_for_path;
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static struct string_list config_fetch_recurse_submodules_for_name;
@@ -388,52 +389,22 @@ void check_for_new_submodule_commits(unsigned char new_sha1[20])
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sha1_array_append(&ref_tips_after_fetch, new_sha1);
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}
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-struct argv_array {
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- const char **argv;
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- unsigned int argc;
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- unsigned int alloc;
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-};
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-
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-static void init_argv(struct argv_array *array)
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-{
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- array->argv = NULL;
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- array->argc = 0;
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- array->alloc = 0;
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-}
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-
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-static void push_argv(struct argv_array *array, const char *value)
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-{
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- ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
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- array->argv[array->argc++] = xstrdup(value);
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- array->argv[array->argc] = NULL;
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-}
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-
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-static void clear_argv(struct argv_array *array)
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-{
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- int i;
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- for (i = 0; i < array->argc; i++)
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- free((char **)array->argv[i]);
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- free(array->argv);
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- init_argv(array);
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-}
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-
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static void add_sha1_to_argv(const unsigned char sha1[20], void *data)
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{
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- push_argv(data, sha1_to_hex(sha1));
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+ argv_array_push(data, sha1_to_hex(sha1));
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}
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static void calculate_changed_submodule_paths(void)
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{
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struct rev_info rev;
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struct commit *commit;
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- struct argv_array argv;
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+ struct argv_array argv = ARGV_ARRAY_INIT;
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init_revisions(&rev, NULL);
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- init_argv(&argv);
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- push_argv(&argv, "--"); /* argv[0] program name */
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+ argv_array_push(&argv, "--"); /* argv[0] program name */
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sha1_array_for_each_unique(&ref_tips_after_fetch,
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add_sha1_to_argv, &argv);
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- push_argv(&argv, "--not");
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+ argv_array_push(&argv, "--not");
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sha1_array_for_each_unique(&ref_tips_before_fetch,
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add_sha1_to_argv, &argv);
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setup_revisions(argv.argc, argv.argv, &rev, NULL);
@@ -460,7 +431,7 @@ static void calculate_changed_submodule_paths(void)
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}
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}
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- clear_argv(&argv);
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+ argv_array_clear(&argv);
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sha1_array_clear(&ref_tips_before_fetch);
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sha1_array_clear(&ref_tips_after_fetch);
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initialized_fetch_ref_tips = 0;