Change the default .argocd-source path

[darklight147]

Describe the bug
The bug am facing is that i have different branches for different environements, preprod, staging, prod, and image updater commit and push to a branch with the .argocd files, means i cannot merge from one branch to another without affecting the deployments of the apps in the other environements

To Reproduce
1- have a branch per environements
2- each app has its app for preprod, staging, prod
3- image updater commits to the same file for all environemnts

Expected behavior
have a way to seperate files by targetRevision, so that the file commited by image updater is something like .argocd-source-preprod-myapp.yaml so that when image updater for a different environement tries to perform an update, it doesnt override the file used by the other envirronements too

Additional context
Add any other context about the problem here.

[chengfang]

Does specifying argocd-image-updater.argoproj.io/write-back-target: xyz help? Each branch and env can have its own write-back-target. The default write-back-target file name already includes application name and namespace name, and we may not want to overload it with too much.