git: Full length SHA-1 in, full length SHA-1 out.

This removes ambiguity at the expense of slight backward incompatibility.
git: Remove unnecessary return code checking.

The functions either return rc=0 or call fail_json themselves.
git: Make function get_remote_head usable when cloning.

This allows the module to return the before/after revisions in all cases.
git: Always return the before/after revisions, even in check mode.

The return values from check mode and non-check mode should match in all cases,
except when a SHA-1 hash is used as version, as there is no way to check if it
is a valid hash using `git ls-remote`.

Also, to accomodate this change, the force flag for the reset function has been
removed so that we can do the checking in main.
git: Handle network problem when running `git ls-remote`.
git: Don't add --branch while cloning if the version is a SHA-1 hash.
Various standardization to the proposed gce_storage module to bring things in line with updates to the S3 module.
Some typo fixes.

Further testing required.
Improve change detection in mysql_variables

mysql_variables bindly executes a SET var = value query even when
the variable already has the requested value.

With this patch the query is executed only if the current value is
different to the requested one.
Fixes #4554 Enumerate user homedir if not passed as an argument
Merge pull request #4568 from mmoya/features

Improve change detection in mysql_variables
Merge pull request #4539 from sayap/git-sha1

git: Always return the before/after revisions, even in check mode.
added aws_access_key and aws_secret_key aliases to ec2_group arguments
Fixes #4402 wrong order for isinstance parameters in dnstxt.py
add_group module: strip trailing/leading whitespace from comma-separated group names
Merge pull request #4571 from tgerla/whitespace

add_group module: strip trailing/leading whitespace from comma-separated group names
Merge pull request #4562 from nimbis/devel

Adding aws_access_key and aws_secret_key aliases to ec2_group arguments
Fixes #4583 enforce that vars_files is a list
fix change_when example for False
Merge pull request #4588 from maxamillion/maxamillion/docfix-changed_when

fix change_when example for False
now correctly changes script permission in all cases

Signed-off-by: Brian Coca <briancoca+ansible@gmail.com>