Suggested improvements to the git-p4 documentation (branch-related)

[Olivier Delalleau <shish@keba.be>]

Hi,

While struggling to get git-p4 to work properly with branches, I
thought the documentation on http://git-scm.com/docs/git-p4 could use
some improvements:

1. At the end of the "Branch detection" section, the following
commands are provided (for when you want to explicitly provide branch
mappings to git-p4):

git config git-p4.branchList main:branch1
git p4 clone --detect-branches //depot@all

The second command should end with a dot (".") because the first
command only works if you are already in a git-initialized folder.
Thus I would also suggest to add "git init" as first command to type.

2. Even though having a "main" branch is standard in Perforce, it
would be worth mentioning what happens when you don't: there is a
message "Could not detect main branch. No checkout/master branch
created" output by the "git p4 clone" command. However, it will still
work if you manually set the master branch ("git checkout -b master
remotes/p4/my_custom_main_branch").

3. I don't know what I missed for that one, but I haven't been able to
get the example for the --branch option to work. It says that after
"git init", we can import a p4 branch with:

git p4 sync --branch=refs/remotes/p4/proj2 //depot/proj2

However, after doing this, followed by "git checkout -b proj2
remotes/p4/proj2", I am unable to properly use "git p4 sync" or "git
p4 submit" from this branch, as git complains about a missing
refs/remotes/p4/master.
Maybe it only works if "git clone" has been used before? But then why
have "git init" first?

NB: it's quite possible some of my problems were caused by me not
properly understanding the doc / how git/p4 works. My apologies if
that's the case.

-=- Olivier