librefetch: support SOURCE_DATE_EPOCH

fixes https://labs.parabola.nu/issues/884

2 files changed, 14 insertions, 4 deletions

diff --git a/src/librefetch/librefetch.8.ronn b/src/librefetch/librefetch.8.ronn
index 5720c8d..cf009de 100644
--- a/src/librefetch/librefetch.8.ronn
+++ b/src/librefetch/librefetch.8.ronn
@@ -184,9 +184,10 @@ The following modifications are made to makepkg:
  * Don't symlink the resulting file into the current directory.
  * <PURGE_TARGETS> interprets an item as a directory if it ends with a
    slash ("/").
- * Timestamps in <$pkgdir> are reset to "1990-01-01 0:0:0 +0", so that
-   the resulting tarball will be the same, regardless of when it was
-   created.
+ * Timestamps in <$pkgdir> are reset to the date specified in
+   <SOURCE_DATE_EPOCH>[1], or "1990-01-01 0:0:0 +0" if it's not set, so
+   that the resulting tarball will be the same, regardless of when it
+   was created.
  * Sort the files included in the tarball; normally the order of files
    in a tarball is essentially random (even if it tends to be the same
    when re-created on the same machine).
@@ -206,3 +207,8 @@ the `librefetch.conf` file.
 ## SEE ALSO
 
 librefetch.conf(5), makepkg(8), PKGBUILD(5), SRCBUILD(5)
+
+## NOTES
+
+ 1. <SOURCE_DATE_EPOCH> specification for build systems
+    https://reproducible-builds.org/specs/source-date-epoch/
diff --git a/src/librefetch/librefetchdir/libmakepkg/tidy/~source_date_epoch.sh b/src/librefetch/librefetchdir/libmakepkg/tidy/~source_date_epoch.sh
index 562820b..fec7686 100755
--- a/src/librefetch/librefetchdir/libmakepkg/tidy/~source_date_epoch.sh
+++ b/src/librefetch/librefetchdir/libmakepkg/tidy/~source_date_epoch.sh
@@ -27,5 +27,9 @@ LIBMAKEPKG_TIDY_SOURCE_DATE_EPOCH_SH=1
 tidy_modify+=('tidy_source_date_epoch')
 
 tidy_source_date_epoch() {
-	find . -exec touch --no-dereference --date="1990-01-01 0:0:0 +0" -- {} +
+	local date='1990-01-01 0:0:0 +0'
+	if [[ -n "$SOURCE_DATE_EPOCH" ]]; then
+		date="@$SOURCE_DATE_EPOCH"
+	fi
+	find . -exec touch --no-dereference --date="$date" -- {} +
 }