Use git-core base pkg instead of git

[macedogm]

Use the base level package git-core that has less dependencies than git, reducing image size and possibly future CVEs ("less packages normally means less CVEs").

git

/ # zypper in git
Refreshing service 'container-suseconnect-zypp'.
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following 12 NEW packages are going to be installed:
  file git git-core less libexpat1 libgdbm4 libpcre2-8-0 libsha1detectcoll1 perl perl-Error perl-Git which

The following 12 packages are not supported by their vendor:
  file git git-core less libexpat1 libgdbm4 libpcre2-8-0 libsha1detectcoll1 perl perl-Error perl-Git which

12 new packages to install.
Overall download size: 12.5 MiB. Already cached: 0 B. After the operation, additional 69.5 MiB will be used.

git-core

/ # zypper in git-core
Refreshing service 'container-suseconnect-zypp'.
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following 7 NEW packages are going to be installed:
  file git-core less libexpat1 libpcre2-8-0 libsha1detectcoll1 which

The following 7 packages are not supported by their vendor:
  file git-core less libexpat1 libpcre2-8-0 libsha1detectcoll1 which

7 new packages to install.
Overall download size: 5.6 MiB. Already cached: 0 B. After the operation, additional 28.5 MiB will be used.

Note (@weyfonk): This PR initially targeted master, hence replaced git with git-core. But it now targets release/fleet/v0.9, where git is not in package/Dockerfile, although it should be.
This PR now effectively acts as a backport of #362 as well.

[weyfonk]

Thanks! Submitted to rancher/fleet as rancher/fleet#2105, as per rancher/fleet#2008.

[macedogm]

@weyfonk thanks! Should I close this PR then?

[weyfonk]

@weyfonk thanks! Should I close this PR then?

No need :) As discussed offline, this is still relevant for Fleet v0.9.

[weyfonk]

CI fails because it runs against a fork which doesn't have access to secrets. It passes when running against the same state on the upstream repository.