fix: support underscores in package version strings

src/downgrade

@@ -164,12 +164,12 @@ filter_packages() {
 matches_name_version_filter() {
   local pkg=$1 name=$2 operator=$3 search_version=$4 pkg_version version_regex
 
-  if [[ -z "$operator" ]] || [[ -z "$version" ]]; then
+  if [[ -z "$operator" ]] || [[ -z "$search_version" ]]; then
     return 0
   fi
 
   # version: 2025.11.12.r15.g0eed3fe
-  version_regex="[a-zA-Z0-9.]+"
+  version_regex="[a-zA-Z0-9._]+"
   hash_or_minor="([0-9]+|[a-z0-9]{6,})"
   pkg_version=$(sed -r "s/.*$name-($version_regex)(-$hash_or_minor)?-(any|$DOWNGRADE_ARCH)\\.(git)?pkg\\.tar\\.(gz|xz|zst)/\1\2/g" <<<"$pkg")
   cmp=$(vercmp "$pkg_version" "$search_version")
@@ -249,7 +249,7 @@ search_cache() {
   local name=$1 pkgfile_re index
 
   # version: 2025.11.12.r15.g0eed3fe
-  version_regex="[a-zA-Z0-9.]+"
+  version_regex="[a-zA-Z0-9._]+"
   hash_or_minor="([0-9]+|[a-z0-9]{6,})"
   pkgfile_re="$name-($version_regex)(-$hash_or_minor)?-(any|$DOWNGRADE_ARCH)\\.pkg\\.tar\\.(gz|xz|zst)"
 
@@ -569,7 +569,7 @@ build_pkg() {
   local item="$1" path commit_hash build_failed versionreg hashreg gitpkgreg
   if [[ "$item" =~ .*gitpkg.tar.gz ]]; then
     # version: 2025.11.12.r15.g0eed3fe
-    versionreg="([a-zA-Z0-9]+\.?)*"
+    versionreg="([a-zA-Z0-9_]+\.?)*"
     hashreg='[a-z0-9]{6,}'
     #hash_or_minor="-([0-9]+|[a-z0-9]{6,})" # leaving this as a note, only hash should appear tho
     gitpkgreg="(.*)-$versionreg-($hashreg)-(any|$DOWNGRADE_ARCH).gitpkg.tar.gz"

test/build_pkg/underscore_version.t

@@ -0,0 +1,26 @@
+  $ source "$TESTDIR/../helper.sh"
+  > mkdir -p "$TMP/build_test"
+  > cd "$TMP/build_test"
+  > touch PKGBUILD
+
+Mock git, makepkg and su
+  $ su() {
+  >   local cmd
+  >   while [[ $# -gt 0 ]]; do
+  >     if [[ "$1" == "-c" ]]; then cmd="$2"; break; fi
+  >     shift
+  >   done
+  >   case "$cmd" in
+  >     *"makepkg -fs"*) touch "$TMP/build_test/pkg-1.2_3-1-any.pkg.tar.gz"; return 0 ;;
+  >     git*) return 0 ;;
+  >     "makepkg --packagelist") echo "$TMP/build_test/pkg-1.2_3-1-any.pkg.tar.gz" ;;
+  >   esac
+  > }
+  > stat() { echo "testuser"; }
+  > export -f su stat
+
+It builds package with underscore in version
+  $ item="$TMP/build_test/pkg-1.2_3-abcdef-any.gitpkg.tar.gz"
+  > build_pkg "$item"
+  > cat new_to_install.downgrade | tr '\0' '\n'
+  /tmp/*/build_test/pkg-1.2_3-1-any.pkg.tar.gz (glob)

test/main/matches_name_version_filter.t

@@ -0,0 +1,21 @@
+  $ source "$TESTDIR/../helper.sh"
+
+It matches standard version
+  $ matches_name_version_filter "pkg-1.0.0-1-any.pkg.tar.gz" "pkg" "=" "1.0.0" && echo "match" || echo "no match"
+  match
+
+It matches version with underscore
+  $ matches_name_version_filter "pkg-1.2_3-1-any.pkg.tar.gz" "pkg" "=" "1.2_3" && echo "match" || echo "no match"
+  match
+
+It does not match different version with underscore
+  $ matches_name_version_filter "pkg-1.2_3-1-any.pkg.tar.gz" "pkg" "=" "1.2_4" && echo "match" || echo "no match"
+  no match
+
+It handles operators with underscore versions (>=)
+  $ matches_name_version_filter "pkg-1.2_5-1-any.pkg.tar.gz" "pkg" ">=" "1.2_3" && echo "match" || echo "no match"
+  match
+
+It handles operators with underscore versions (<)
+  $ matches_name_version_filter "pkg-1.2_3-1-any.pkg.tar.gz" "pkg" "<" "1.2_5" && echo "match" || echo "no match"
+  match

test/search_cache/specific-version.t

@@ -83,3 +83,11 @@ With a version string included
   > DOWNGRADE_FROM_CACHE=1 search_cache 'foo' | filter_packages 'foo' '<' '2.0-1' | sort
   /tmp/*/foo-1.0-1-any.pkg.tar.gz (glob)
   /tmp/*/foo-1.1-1-any.pkg.tar.gz (glob)
+
+It finds packages with underscores in version
+  $ cache=$(mktemp -d)
+  > touch "$cache/pkg-1.2_3-1-any.pkg.tar.gz"
+  > touch "$cache/pkg-1.2-1-any.pkg.tar.gz"
+  > write_pacman_conf "[options]" "CacheDir = $cache/"
+  > DOWNGRADE_FROM_CACHE=1 search_cache 'pkg' | filter_packages 'pkg' '=' '1.2_3-1' | sort
+  /tmp/*/pkg-1.2_3-1-any.pkg.tar.gz (glob)