Recognize upstream pre-release versions

so that tilde '~' instead of '-' is used in upstream tarball
and in debian/changelog, e.g. 1.0.0~rc1 instead of 1.0.0-rc.1

Thanks: nicoo
Closes: #981421

Author: anthonyfok

template.go

@@ -318,14 +318,14 @@ func writeDebianWatch(dir, gopkg, debsrc string, hasRelease bool, repack bool) e
 	}
 	defer f.Close()
 
-	filenamemanglePattern := `s%%(?:.*?)?v?(\d[\d.]*)\.tar\.gz%%%s-$1.tar.gz%%`
-	uversionmanglePattern := `s/(\d)[_\.\-\+]?(RC|rc|pre|dev|beta|alpha)[.]?(\d*)$/\$1~\$2\$3/`
+	filenamemanglePattern := `s%(?:.*?)?v?(\d[\d.]*)\.tar\.gz%@PACKAGE@-$1.tar.gz%`
+	uversionmanglePattern := `s/(\d)[_\.\-\+]?(RC|rc|pre|dev|beta|alpha)[.]?(\d*)$/$1~$2$3/`
 
 	if hasRelease {
 		log.Printf("Setting debian/watch to track release tarball")
-		fmt.Fprintf(f, "version=4\n")
-		fmt.Fprintf(f, `opts="filenamemangle=`+filenamemanglePattern+`,\`+"\n", debsrc)
-		fmt.Fprintf(f, `      uversionmangle=`+uversionmanglePattern)
+		fmt.Fprint(f, "version=4\n")
+		fmt.Fprint(f, `opts="filenamemangle=`+filenamemanglePattern+`,\`+"\n")
+		fmt.Fprint(f, `      uversionmangle=`+uversionmanglePattern)
 		if repack {
 			fmt.Fprintf(f, `,\`+"\n")
 			fmt.Fprintf(f, `      dversionmangle=s/\+ds\d*$//,repacksuffix=+ds1`)

version.go

@@ -20,6 +20,11 @@ var (
 	// from https://semver.org/#is-there-a-suggested-regular-expression-regex-to-check-a-semver-string
 	// with leading "v" added.
 	semverRegexp = regexp.MustCompile(`^v(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$`)
+
+	// uversionPrereleaseRegexp checks for upstream pre-release
+	// so that '-' can be replaced with '~' in pkgVersionFromGit.
+	// To be kept in sync with the regexp portion of uversionmanglePattern in template.go
+	uversionPrereleaseRegexp = regexp.MustCompile(`(\d)[_\.\-\+]?(RC|rc|pre|dev|beta|alpha)[.]?(\d*)$`)
 )
 
 // pkgVersionFromGit determines the actual version to be packaged
@@ -66,9 +71,15 @@ func pkgVersionFromGit(gitdir string, u *upstream, forcePrerelease bool) (string
 		}
 
 		u.commitIsh = latestTag
-		u.version = strings.TrimLeftFunc(latestTag, func(r rune) bool {
-			return !unicode.IsNumber(r)
-		})
+
+		// Mangle latestTag into Debian upstream_version
+		// TODO: Move to function and write unit test?
+		u.version = strings.TrimLeftFunc(
+			uversionPrereleaseRegexp.ReplaceAllString(latestTag, "$1~$2$3"),
+			func(r rune) bool {
+				return !unicode.IsNumber(r)
+			},
+		)
 
 		if forcePrerelease {
 			log.Printf("INFO: Force packaging master (prerelease) as requested by user")