Improve error messages for spago publish

[JordanMartinez]

Description of the change

Fixes #1108.

These changes may still cause someone to run spago publish a few times before they fix every error, but it should prevent unpublishable git tags. The idea is:

• show all errors, but put the git-tag-related ones at the bottom with a note saying to resolve all other errors and to not push any created git tags
• move the Git.pushTags call, which requires login credentials to a step before the actual publish
• I added another check for when the current publish config refers to an existing tag, but we don't have it checked out.

Checklist:

• Added the change to the "Unreleased" section of the changelog
• Added some example of the new feature to the README
• Added a test for the contribution (if applicable)

P.S.: the above checks are not compulsory to get a change merged, so you may skip them. However, taking care of them will result in less work for the maintainers and will be much appreciated 😊

[f-f]

This error is considerably worse than the one we were giving out before - can we improve it?

[JordanMartinez]

Should I also update the Git.listTags to use message rather than shortMessage?

[f-f]

I don't think shortMessage vs message is going to matter here - the previous error message for the same test case was pretty informative:

❌ The git tree is not clean, or you haven't checked out the tag you want to publish.
Command failed with exit code 128: git status --porcelain
Please commit or stash your changes, and checkout the tag you want to publish.
fatal: not a git repository (or any of the parent directories): .git
To create the tag, you can run:
  git tag v0.0.1

The current one (even with message) much less so:

❌ Could not run `git status`. Error:
Command failed with exit code 128: git status --porcelain
fatal: not a git repository (or any of the parent directories): .git

I'd be pretty confused myself if I got this error.
It looks like we should catch the error where we have the context to give a good explanation, rather than just throwing the error that comes from git.

(to clarify - the old error message was not perfect either. We are still reporting the message that comes from git, but I think that's still confusing. The informative part of this is probably the only one we should show, and print the rest with debug logging: The git tree is not clean, or you haven't checked out the tag you want to publish.)

[JordanMartinez]

Three things.
First, it's not clear to me why this test originally reported the above error. The "The git tree is not clean, or you haven't checked out the tag you want to publish.)" message is only reported when git status succeeds. If git status failed, it would just die there. So, what changes did I make that caused that to change?

Second, while I can mention the "git tree is not clean" part, checking out the tag shouldn't be done until the other issues are resolved first.

Third, printing the git status error as a debug message (as I'm understanding your last sentence) seems erroneous, too. If git status fails, there's a larger issue at hand (like the fact that no git repo exists) that should be reported to the user. Saying the 'git tree is not clean' misses the point. So, I updated the message to clarify why we were running git status.

[f-f]

This is all good, but I still think this warrants further investigation to improve error messages - I mean, we have a test that consistently reproduces a situation where a user gets a bad error message. We don't need to report that the user needs to make a tag at that point, but it should be clearly actionable, which it's not at the moment

[JordanMartinez]

Meaning... we should tell the user to run git init in this case?

[f-f]

git status will return an exit code 128 in various situations (no git repository available, or it's there but it's owned by another user, etc), but the most common reason is by far "there's no git repo".
So we should figure out that a 128 was returned and tell the user "Spago could not run git status because there's no git repo. Please run git init and commit your source files to move forward" (or something like that). We don't need to report the error message coming from git, we are pretty sure of what's going on.