lint: check label style only on changed files

This should probably propagate to the other lint checks.
The idea: only enforce style on files that were at least touched
by the developer.

Change-Id: I5ac690ee726e27e80e790fa9a41cd14b84ad2161
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/4644
Tested-by: build bot (Jenkins)
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/util/lint/lint-stable-004-style-labels b/util/lint/lint-stable-004-style-labels
index 31ad74e..10b0408 100755
--- a/util/lint/lint-stable-004-style-labels
+++ b/util/lint/lint-stable-004-style-labels
@@ -19,4 +19,4 @@
 # DESCR: Check that C labels begin at start-of-line
 
 LC_ALL=C export LC_ALL
-find src -name '*.[scS]' -exec grep '^[[:space:]][[:space:]]*[a-z][a-z]*:[[:space:]]*$' {} + |grep -v "[^a-z_]default:"
+git diff --name-status |grep -v "^D" |cut -c3- |grep "^src/.*\.[csS]" | xargs grep -Hn '^[[:space:]][[:space:]]*[a-z][a-z]*:[[:space:]]*$' |grep -v "[^a-z_]default:"