Improve errors for failed "zapi load"

[jameskerr]

I am trying to ingest data from standard in using zapi load. I'm getting an error that is hard to debug like so:

My command (without a -use):

echo '{hello: "world"}' | zapi load -

Output:

HEAD not specified: indicate with -use or run the "use" command

So I add my use (without a branch):

echo '{hello: "world"}' | zapi load -use Demo -

And I get the same error:

HEAD not specified: indicate with -use or run the "use" command

Finally, I add @main and it works.

echo '{hello: "world"}' | zapi load -use Demo@main -
21mrhnKXzluy8ZftzB6cuzqoZhE committed

It seems like this should either work without the branch name, or it should give an error saying, "Pool name provided but no branch. The -use value must be have the form pool@commit or pool@branch."

[philrz]

We've improved significantly since this issue was opened. Here's a walk through the equivalent repro steps using current Zed commit 26dbda03:

$ zed -version
Version: v1.2.0-20-g26dbda03

$ ls -l ~/.zed_head
ls: /Users/phil/.zed_head: No such file or directory

$ echo '{hello: "world"}' | zed load -
empty pool and branch

$ echo '{hello: "world"}' | zed load -use Demo -
"Demo": pool not found

$ zed create Demo
pool created: Demo 2CXc43SnRlIK7D7shSKbT4DsB8N

$ echo '{hello: "world"}' | zed load -use Demo -
(12/1) 17B 17B/s
2CXc4Pev5XDs5zFlGBpQQKdSGKc committed

In conclusion:

1. The zed load does now work without having to specify the branch name
2. If we attempt to load to a pool that doesn't exist, we do now get the more helpful "Demo": pool not found error message
3. For the first attempted load when there was neither -use specified nor a ~/.zed_head present, the empty pool and branch error message could probably be improved

I'll keep this one open while we discuss what might be done about that third item.