makepkg: add the $startdir to package .BUILDINFO

This value is needed for reproducible builds. The reason is because
$BUILDDIR changes its behavior depending on whether it is the same as
$startdir, and the result is that we cannot know whether $srcdir (the
path that is potentially embedded into the final package) is actually
"$BUILDDIR/src" or "$BUILDDIR/$pkgbase/src".
Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

doc/BUILDINFO.5.asciidoc

@@ -53,6 +53,9 @@ BUILDINFO file format.
 *builddir*::
 	The directory where the package was built.
 
+*startdir*::
+	The directory from which makepkg was executed.
+
 *buildenv (array)*::
 	The build environment specified in makepkg.conf.
 

scripts/makepkg.sh.in

@@ -626,7 +626,7 @@ write_pkginfo() {
 }
 
 write_buildinfo() {
-	write_kv_pair "format" "1"
+	write_kv_pair "format" "2"
 
 	write_kv_pair "pkgname" "$pkgname"
 	write_kv_pair "pkgbase" "$pkgbase"
@@ -643,6 +643,7 @@ write_buildinfo() {
 	write_kv_pair "packager" "${PACKAGER}"
 	write_kv_pair "builddate" "${SOURCE_DATE_EPOCH}"
 	write_kv_pair "builddir"  "${BUILDDIR}"
+	write_kv_pair "startdir"  "${startdir}"
 	write_kv_pair "buildenv" "${BUILDENV[@]}"
 	write_kv_pair "options" "${OPTIONS[@]}"