JENKINS-63487 Clarifying local branch name for detached checkouts

[patricklangsonos]

The documentation doesn't clearly state what the behavior is if you:

1. check out a given revision from a Git repo and
2. set Checkout to specific local branch to ** or blank to get an automatic local branch name

16:09:31 Selected Git installation does not exist. Using Default
16:09:31 using credential gh-cred
16:09:31 Cloning the remote Git repository
16:09:32 Cloning repository https://github.com/user/repo.git
16:09:32  > git init /home/build-stage/jenkins/workspace/repo # timeout=10
16:09:32 Fetching upstream changes from https://github.com/user/repo.git
16:09:32  > git --version # timeout=10
16:09:32 using GIT_ASKPASS to set credentials gh-cred
16:09:32  > git fetch --tags --force --progress -- https://github.com/user/repo.git +refs/heads/*:refs/remotes/origin/* # timeout=10
16:10:34  > git config remote.origin.url https://github.com/user/repo.git # timeout=10
16:10:34  > git config --add remote.origin.fetch +refs/heads/*:refs/remotes/origin/* # timeout=10
16:10:35  > git config remote.origin.url https://github.com/user/repo.git # timeout=10
16:10:35 Fetching upstream changes from https://github.com/user/repo.git
16:10:35 using GIT_ASKPASS to set credentials gh-cred
16:10:35  > git fetch --tags --force --progress -- https://github.com/user/repo.git +refs/heads/*:refs/remotes/origin/* # timeout=10
16:10:35  > git rev-parse de7de0c226225101234567894c51e703730e392c^{commit} # timeout=10
16:10:35 Checking out Revision de7de0c226225101234567894c51e703730e392c (detached)
16:10:35 Enabling Git LFS pull
16:10:35  > git config core.sparsecheckout # timeout=10
16:10:35  > git checkout -f de7de0c226225101234567894c51e703730e392c # timeout=10
16:11:36  > git branch -a -v --no-abbrev # timeout=10
16:11:36  > git checkout -b detached de7de0c226225101234567894c51e703730e392c # timeout=10
16:11:36  > git config --get remote.origin.url # timeout=10
16:11:36 using GIT_ASKPASS to set credentials Jenkins integration user for Artifactory
16:11:36  > git lfs pull origin # timeout=10

Checklist

• I have referenced the Jira issue related to my changes in one or more commit messages
• Documentation in README has been updated as necessary

Types of changes

Doc change only

[MarkEWaite]

Formatting alternative proposal to continue existing formatting convention