Reexecuting do_fetch after do_unpack failed with reference is not a tree

Hi,

I guess this will be hard to fix correctly, but please comment if I've overlooked something:

1) update foo git repository with new commit ABCD, but forget to push it
2) bump SRCREV in foo.bb to ABCD
3) run bitbake foo, it will run do_fetch to catch new changes in remote repo, but ABCD is not there, so do_unpack will fail like this:

NOTE: Running task 2289 of 4227 (ID: 1185, foo.bb, do_unpack)
NOTE: recipe foo-1.0+gitr2+ABCD: task do_unpack: Started
ERROR: Function failed: Fetcher failure: Fetch command failed with exit code 128, output:
fatal: reference is not a tree: ABCD

4) realize missing "git push" in step 1) and push it now
5) run bitbake foo again, but do_unpack is still failing, because do_fetch checksums is the same (nothing changed in metadata) so stamp is still valid.

6) fix it with "bitbake -c fetch -f foo", but that could be complicated if bump SRCREV was pushed already and possibly many builders already executed do_fetch, so maybe push PR bump or something like that.

Only better solution than 6) I can think of, is to detect "fatal: reference is not a tree" in do_unpack and if it's git repository then remove do_fetch stamp and hope it was fixed in remote git repo.

I guess this will be hard to fix correctly, but please comment if I've overlooked something:

1) update foo git repository with new commit ABCD, but forget to push it
2) bump SRCREV in foo.bb to ABCD
3) run bitbake foo, it will run do_fetch to catch new changes in remote repo, but ABCD is not there, so do_unpack will fail like this:

NOTE: Running task 2289 of 4227 (ID: 1185, foo.bb, do_unpack)
NOTE: recipe foo-1.0+gitr2+ABCD: task do_unpack: Started
ERROR: Function failed: Fetcher failure: Fetch command failed with exit
code 128, output: fatal: reference is not a tree: ABCD

4) realize missing "git push" in step 1) and push it now
5) run bitbake foo again, but do_unpack is still failing, because do_fetch checksums is the same (nothing changed in metadata) so stamp is still valid.

6) fix it with "bitbake -c fetch -f foo", but that could be complicated if bump SRCREV was pushed already and possibly many builders already executed do_fetch, so maybe push PR bump or something like that.

Only better solution than 6) I can think of, is to detect "fatal: reference is not a tree" in do_unpack and if it's git repository then remove do_fetch stamp and hope it was fixed in remote git repo.