Add quotes around option values with hash in git config files

[mbirbeck]

This is a fix for #309 'Can't clone branch ref name with hash/number sign (#)'

The problem is occurring because the # character in a git config file is interpreted as a comment.

When a repository is cloned a config file is created in the .git directory. I have mocked up an example below by hand:

[core]
	bare = false # This is just a comment so is ignored
[remote "origin"]
	url = https://https://github.com/myrepo.git
	fetch = +refs/heads/release/mybranchname:refs/remotes/origin/release/mybranchname

However, if there is a # character in the branch name like this:

[core]
	bare = false # This is just a comment so is ignored
[remote "origin"]
	url = https://https://github.com/myrepo.git
	fetch = +refs/heads/release/my#branchname:refs/remotes/origin/release/my#branchname

When go-git reads back the file it ignores everything after the # character, so the value read for the fetch option, rather than looking like this:

+refs/heads/release/my#branchname:refs/remotes/origin/release/my#branchname

It is read back from the file as this:

+refs/heads/release/my

go-git then returns an error 'malformed refspec, separators are wrong' because it is expecting at least one ':' separator character in that value.

The fix is to add quotes when encoding that file, so it looks like this:

[core]
	bare = false # This is just a comment so is ignored
[remote "origin"]
	url = https://https://github.com/myrepo.git
	fetch = "+refs/heads/release/my#branchname:refs/remotes/origin/release/my#branchname"

Then when reading and decoding that file go-git gets the correct value.

[adrian-kiwibank]

There are more characters that could cause problems with config values.
Also see #354(plumbing: config, Branch name with hash can be cloned. Fixes #309) for an approved PR for this issue.

[mcuadros]

I merged #354 , thanks for your time.