Don't clean git repository when not needed

[olblak]

Fix #105

This PR improve several things:

• Add a clean parameter for the diff subcommand like updatecli diff --clean=true
• By default delete the temporary directory content at the end of a full run instead of per strategy run, so we only clone git repositories once
• Change --clean parameter to keep or delete the main working directory instead of per repository

This PR drastically drastically improve performances, I tested on jenkins-infra/charts

Before:
updatecli apply --config updateCli/updateCli.d --values updateCli/values.yaml 39,12s user 6,91s system 43% cpu 1:45,92 total
After:
updatecli apply --config updateCli/updateCli.d --values updateCli/values.yaml 30,29s user 3,60s system 66% cpu 51,092 total

[jetersen]

Hmm the cleaning of the directory is one speed improvement.

I however think another place is to perform clone only once perhaps by determinering each repository that would need a clone and than just use git checkout $branch to reset the working directory before each operation.

https://github.com/olblak/updatecli/blob/4f51ca1e20eca618823f1ff207d67cf6dccd0ba5/pkg/engine/target/main.go#L88

[olblak]

Hmm the cleaning of the directory is one speed improvement.

I however think another place is to perform clone only once perhaps by determinering each repository that would need a clone and than just use git checkout $branch to reset the working directory before each operation.

https://github.com/olblak/updatecli/blob/4f51ca1e20eca618823f1ff207d67cf6dccd0ba5/pkg/engine/target/main.go#L88

That's a good point, thanks for the suggestion. It won't be too hard to do that and it will be useful for later stages.

[olblak]

Cloning the repository once requires some refactoring so I am going to merge this one and then a new one when ready