Add CLI switch for legacy overrides

Add CLI switch to maintain compatability with legacy override
syntax via use of flag (-l, --legacy-overrides).

The first implemented example is to swtich from PV:append to PV_append.

src/main.rs

@@ -136,6 +136,10 @@ struct Args {
     /// Reproducible mode: Output exact git references for git projects
     #[structopt(short = "R")]
     reproducible: bool,
+
+    /// Legacy Overrides: Use legacy override syntax
+    #[structopt(short = "l", long = "--legacy-overrides")]
+    legacy_overrides: bool,
 }
 
 #[derive(StructOpt, Debug)]
@@ -356,9 +360,14 @@ fn real_main(options: Args, config: &mut Config) -> CliResult {
     // if this is not a tag we need to include some data about the version in PV so that
     // the sstate cache remains valid
     let git_srcpv = if !project_repo.tag && project_repo.rev.len() > 10 {
+        let mut pv_append_key = "PV:append";
+        // Override PV override with legacy syntax if flagged
+        if options.legacy_overrides {
+            pv_append_key = "PV_append";
+        }
         // we should be using ${SRCPV} here but due to a bitbake bug we cannot. see:
         // https://github.com/meta-rust/meta-rust/issues/136
-        format!("PV:append = \".AUTOINC+{}\"", &project_repo.rev[..10])
+        format!("{} = \".AUTOINC+{}\"", pv_append_key, &project_repo.rev[..10])
     } else {
         // its a tag so nothing needed
         "".into()