'version string generation failed' on deploy

[Stuart Bishop]

With 2.4.2, I've started seeing spurious (?) warnings when deploying:

$ juju deploy ~/charms/repo/builds/postgresql
WARNING version string generation failed : exit status 128

Deploying charm "local:bionic/postgresql-2".

Everything seems to be working fine, despite the noise.

[Ian Booth (wallyworld)]

The issue here is that we now run "git describe --dirty" to pick up the sha of the latest commit and include that in a version file in the charm archive. This is reported in juju status.

However, it seems git describe can sometimes fail with error code 128 if it can't find any suitable tags. Using --always should fix this.

Note that it is just noise in that if there's an error running git describe, the charm deploy still goes ahead.

[Junien F (axino)]

This is still a problem in 2.5-rc1. I believe this could be due to the fact that the "git" command is not run in the appropriate directory.

[Nam Nguyen (nammn)]

Yes, i could recreate the error. if you deploy from a folder which not contains a `.git` folder, this error occurs. So ` nam:~ $ juju deploy ./Workspace/charms/postgresql-charm` leads to it, while
`nam:/home/nam/charm-folder/pogresgit $.... deploy` does not.

[Nam Nguyen (nammn)]

So the kind of stacktrace is the following:

https://github.com/juju/juju/blob/857bf735ef592474eac6c529b27004e791170d19/api/client.go#L336
calls with archive information of the charm
https://github.com/juju/charm/blob/v6/charmdir.go#L248
calls tries to find out the vcs
https://github.com/juju/charm/blob/v6/charmdir.go#L435
find out the path and "just" calls for git case, "git describe --dirty --always" from the cwd.
Thus if the cwd does not contain a ".git" this error should return.

Even "worse" if this is called from a folder with ".git" but which does not belong to the charm the versionstring could be wrong.

The error message itself is a little missleading as we "just" catch the error and generate our own message. The actual error message is:

```
fatal: not a git repository (or any of the parent directories): .git
```

[Nam Nguyen (nammn)]

pr: https://github.com/juju/charm/pull/293