Update guide_gce.rst

Clarify which of the options to pick.
Update the GCE guide with a working configuration.

Also remove a few whitespaces, improve the bash script and fix a typo.
Update community.rst

Fixes https://github.com/ansible/ansible/issues/9202
Update playbooks_roles.rst

Fixes https://github.com/ansible/ansible/issues/7241
Resolve issue where repo_path contains multiple '.git' strings

If the repo_path contained multiple '.git' strings, the _git_repo_info()
call resulted in a traceback.  This change removes the trailing '.git'
and resolves the traceback.
Small typo in galaxy.rst

other SCM sourced in line 96
broken link in developing_modules.rst

link to core modules source is broken since restructuring of public ansible repos
Update developing_modules.rst

The existing description does not make 2 things clear.
1) This is an environment variable
2) It must be set on the _controlling_ host, not the remote host.
Merge pull request #9214 from nmadhok/patch-1

Update community.rst
Merge pull request #9220 from jlaska/devel

Resolve issue where repo_path contains multiple '.git' strings
Merge pull request #9228 from wsuff/patch-1

Small typo in galaxy.rst
Merge pull request #9229 from wjimenez5271/patch-1

broken link in developing_modules.rst
Merge pull request #9234 from gamename/patch-1

Update developing_modules.rst
Merge pull request #9207 from rasputnik/patch-2

Update guide_gce.rst
Merge pull request #9209 from franckcuny/gce-doc

Update the GCE guide with a working configuration.
Add doc of @filename in intro_patterns.rst

I noticed that the @filename notation for the --limit argument was not
conveniently described.

This patch adds a simple example to the intro_patterns.rst file.
Fix several it's/its errors in the documentation.
Creating initial framework for refactoring core codebase
Signatures
Some signature related things, prior to starting test scaffolding