makepkg: respect $SOURCE_DATE_EPOCH to activate reproducible builds

If SOURCE_DATE_EPOCH is set, `touch` all source files between the (optional)
prepare() and build() functions to unify the modification times. This works
around build systems and compilers that embed the file modification times
into the file contents of release artifacts.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/scripts/makepkg.sh.in b/scripts/makepkg.sh.in
index 20e9dd7e..a466e4f1 100644
--- a/scripts/makepkg.sh.in
+++ b/scripts/makepkg.sh.in
@@ -79,6 +79,7 @@ PKGFUNC=0
 PKGVERFUNC=0
 PREPAREFUNC=0
 REPKG=0
+REPRODUCIBLE=0
 RMDEPS=0
 SKIPCHECKSUMS=0
 SKIPPGPCHECK=0
@@ -87,7 +88,12 @@ SPLITPKG=0
 SOURCEONLY=0
 VERIFYSOURCE=0
 
-export SOURCE_DATE_EPOCH=${SOURCE_DATE_EPOCH:-$(date +%s)}
+if [[ -n $SOURCE_DATE_EPOCH ]]; then
+	REPRODUCIBLE=1
+else
+	SOURCE_DATE_EPOCH=$(date +%s)
+fi
+export SOURCE_DATE_EPOCH
 
 PACMAN_OPTS=()
 
@@ -1686,6 +1692,11 @@ if (( !REPKG )); then
 		if (( PREPAREFUNC )); then
 			run_prepare
 		fi
+		if (( REPRODUCIBLE )); then
+			# We have activated reproducible builds, so unify source times before
+			# building
+			find "$srcdir" -exec touch -h -d @$SOURCE_DATE_EPOCH {} +
+		fi
 	fi
 
 	if (( PKGVERFUNC )); then