internal/rosa: wrapper around git helper

This results in much cleaner call site for the majority of use cases.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/libbsd.go

@@ -7,10 +7,9 @@ func (t Toolchain) newLibmd() (pkg.Artifact, string) {
 		version  = "1.1.0"
 		checksum = "9apYqPPZm0j5HQT8sCsVIhnVIqRD7XgN7kPIaTwTqnTuUq5waUAMq4M7ev8CODJ1"
 	)
-	return t.NewPackage("libmd", version, t.NewViaGit(
+	return t.NewPackage("libmd", version, t.newTagRemote(
 		"https://git.hadrons.org/git/libmd.git",
-		"refs/tags/"+version,
-		mustDecode(checksum),
+		version, checksum,
 	), nil, &MakeHelper{
 		Generate: "echo '" + version + "' > .dist-version && ./autogen",
 		ScriptMakeEarly: `
@@ -38,10 +37,9 @@ func (t Toolchain) newLibbsd() (pkg.Artifact, string) {
 		version  = "0.12.2"
 		checksum = "NVS0xFLTwSP8JiElEftsZ-e1_C-IgJhHrHE77RwKt5178M7r087waO-zYx2_dfGX"
 	)
-	return t.NewPackage("libbsd", version, t.NewViaGit(
+	return t.NewPackage("libbsd", version, t.newTagRemote(
 		"https://gitlab.freedesktop.org/libbsd/libbsd.git",
-		"refs/tags/"+version,
-		mustDecode(checksum),
+		version, checksum,
 	), nil, &MakeHelper{
 		Generate: "echo '" + version + "' > .dist-version && ./autogen",
 	},