[PATCH 1/4] Fix maybe-uninitialized warning with GCC at -O3

[Mike Hommey <mh@xxxxxxxxxxxx>]

```
In file included from parse-options.c:1:
git-compat-util.h: In function ‘get_value’:
git-compat-util.h:489:21: error: ‘arg’ may be used uninitialized [-Werror=maybe-uninitialized]
  489 | #define error(...) (error(__VA_ARGS__), const_error())
      |                     ^~~~~
parse-options.c:76:21: note: ‘arg’ was declared here
   76 |         const char *arg;
      |                     ^~~
```

Signed-off-by: Mike Hommey <mh@xxxxxxxxxxxx>
---
 parse-options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/parse-options.c b/parse-options.c
index a9a39ecaef..cf79805bc0 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -73,7 +73,7 @@ static enum parse_opt_result do_get_value(struct parse_opt_ctx_t *p,
 					  enum opt_parsed flags,
 					  const char **argp)
 {
-	const char *arg;
+	const char *arg = NULL;
 	const int unset = flags & OPT_UNSET;
 	int err;
 
-- 
2.50.0.rc1.593.g042f21cb9b