ci: run a pedantic build as part of the GitHub workflow

similar to the recently added sparse task, it is nice to know as early
as possible.

add a dockerized build using fedora (that usually has the latest gcc)
to be ahead of the curve and avoid older ISO C issues at the same time.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.github/workflows/main.yml

@@ -324,6 +324,8 @@ jobs:
           image: alpine
         - jobname: Linux32
           image: daald/ubuntu32:xenial
+        - jobname: pedantic
+          image: fedora
     env:
       jobname: ${{matrix.vector.jobname}}
     runs-on: ubuntu-latest

ci/install-docker-dependencies.sh

@@ -15,4 +15,8 @@ linux-musl)
 	apk add --update build-base curl-dev openssl-dev expat-dev gettext \
 		pcre2-dev python3 musl-libintl perl-utils ncurses >/dev/null
 	;;
+pedantic)
+	dnf -yq update >/dev/null &&
+	dnf -yq install make gcc findutils diffutils perl python3 gettext zlib-devel expat-devel openssl-devel curl-devel pcre2-devel >/dev/null
+	;;
 esac

ci/run-build-and-tests.sh

@@ -10,6 +10,11 @@ windows*) cmd //c mklink //j t\\.prove "$(cygpath -aw "$cache_dir/.prove")";;
 *) ln -s "$cache_dir/.prove" t/.prove;;
 esac
 
+if test "$jobname" = "pedantic"
+then
+	export DEVOPTS=pedantic
+fi
+
 make
 case "$jobname" in
 linux-gcc)
@@ -35,10 +40,9 @@ linux-clang)
 	export GIT_TEST_DEFAULT_HASH=sha256
 	make test
 	;;
-linux-gcc-4.8)
+linux-gcc-4.8|pedantic)
 	# Don't run the tests; we only care about whether Git can be
-	# built with GCC 4.8, as it errors out on some undesired (C99)
-	# constructs that newer compilers seem to quietly accept.
+	# built with GCC 4.8 or with pedantic
 	;;
 *)
 	make test