msys2-runtime(update-patches): determine the base tag automatically

When upgrading to a newer upstream version, we cannot rely on the base
tag that is recorded in the PKGBUILD file.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

msys2-runtime/update-patches.sh

@@ -17,7 +17,7 @@ die "Clean worktree required"
 git rm 0*.patch ||
 die "Could not remove previous patches"
 
-base_tag=refs/tags/cygwin-"$(sed -n -e 's/^pkgver=//p' <PKGBUILD)"
+base_tag=refs/tags/"$(expr "$(git -C src/msys2-runtime/ describe --tags HEAD)" : '^\(cygwin-[0-9.]*\)')"
 source_url=$(sed -ne 's/git+https:/https:/' -e 's/^source=\([^:]\+::\)\?["'\'']\?\([^"'\''#?=&,;[:space:]]\+[^)"'\''#?=&,;[:space:]]\).*/\2/p' <PKGBUILD)
 
 git -C src/msys2-runtime fetch --no-tags "$source_url" "$base_tag:$base_tag"
@@ -60,6 +60,7 @@ in_sources="$(echo "$patches" | sed "{s/^/        /;:1;N;s/\\n/\\\\n        /;b1
 in_prepare="$(echo "$patches" | sed -n '{:1;s|^|  |;H;${x;s/\n/ \\\\\\n/g;p;q};n;b1}')"
 sed -i -e "/^        0.*\.patch$/{:1;N;/[^)]$/b1;s|.*|$in_sources)|}" \
 	-e "/^ *apply_git_am_with_msg .*\\\\$/{s/.*/  apply_git_am_with_msg \\\\/p;:2;N;/[^}]$/b2;s|.*|$in_prepare\\n\\}|}" \
+	-e "s/^\\(pkgver=\\).*/\\1${base_tag#refs/tags/cygwin-}/" \
 	PKGBUILD ||
 die "Could not update the patch set in PKGBUILD"