Forward null when parent cannot be found

[aaron-skydio]

Currently if I run a workflow where the parent commit cannot be found in
the destination (with merge_import from
here
off), I get an exception:

java.util.NoSuchElementException: No value present
        at java.base/java.util.Optional.get(Optional.java:148)
        at com.google.copybara.WorkflowMode$3.run(WorkflowMode.java:261)
        at com.google.copybara.Workflow.run(Workflow.java:288)
        at com.google.copybara.MigrateCmd.run(MigrateCmd.java:92)
        at com.google.copybara.MigrateCmd.run(MigrateCmd.java:69)
        at com.google.copybara.Main.runInternal(Main.java:241)
        at com.google.copybara.Main.run(Main.java:123)
        at com.google.copybara.Main.main(Main.java:102)
ERROR: Unexpected error (please file a bug against copybara): No value present (java.util.NoSuchElementException: No value present)

I think the right thing to do here is convert the empty Optional to
null? In which case I a legitimate error message instead of a crash:

ERROR: Cannot find matching parent commit in the destination. Use '--change-request-parent' flag to force a parent commit to use as baseline in the destination.

Definitely not 100% sure this fix is correct though, this is as much a
bug report as it is a proposed fix.

Topic: copybara-null-baseline

[aaron-skydio]

Reviews in this chain:
└#228 Forward null when parent cannot be found

[aaron-skydio]

#	head	base	diff	date	summary
0	4170f792	f7d77144	diff	Mar 10 18:24 PM	1 file changed, 1 insertion(+), 1 deletion(-)
1	f940dc4e	c7a43cb0	diff	Mar 13 21:18 PM	0 files changed

[aaron-skydio]

About the conflict - I see on main (as of 3af038c) this now doesn't crash, but prints a different error message. It seems like this shouldn't recommend passing --baseline-for-merge-import if merge_import isn't enabled?

[aaron-skydio]

Updated to the actual proposed change to main