[PATCH 6/6] builtin_diff(): read $GIT_DIFF_OPTS closer to use

[Jeff King <peff@peff.net>]

The value returned by getenv() is not guaranteed to remain valid across
other environment function calls. But in between our call and using the
value, we run fill_textconv(), which may do quite a bit of work,
including spawning sub-processes.

We can make this safer by calling getenv() right before we actually look
at its value.

Signed-off-by: Jeff King <peff@peff.net>
---
 diff.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/diff.c b/diff.c
index 15556c190d..6751ec29f0 100644
--- a/diff.c
+++ b/diff.c
@@ -3476,7 +3476,7 @@ static void builtin_diff(const char *name_a,
 		o->found_changes = 1;
 	} else {
 		/* Crazy xdl interfaces.. */
-		const char *diffopts = getenv("GIT_DIFF_OPTS");
+		const char *diffopts;
 		const char *v;
 		xpparam_t xpp;
 		xdemitconf_t xecfg;
@@ -3519,12 +3519,15 @@ static void builtin_diff(const char *name_a,
 			xecfg.flags |= XDL_EMIT_FUNCCONTEXT;
 		if (pe)
 			xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
+
+		diffopts = getenv("GIT_DIFF_OPTS");
 		if (!diffopts)
 			;
 		else if (skip_prefix(diffopts, "--unified=", &v))
 			xecfg.ctxlen = strtoul(v, NULL, 10);
 		else if (skip_prefix(diffopts, "-u", &v))
 			xecfg.ctxlen = strtoul(v, NULL, 10);
+
 		if (o->word_diff)
 			init_diff_words_data(&ecbdata, o, one, two);
 		if (xdi_diff_outf(&mf1, &mf2, NULL, fn_out_consume,
-- 
2.20.1.651.g2d41a78c67