Require gitlib 1.7 and fix its deprecations

[lyrixx]

Q	A
Branch	v2.x
Bug fix?	no
New feature?	no
BC breaks?	The constructor of GitRepository and GitRepositoryLocator::locate(), see below
Deprecations?	no
Documented?	no
Fixed tickets

gitlib 1.7 prepares the upgrade to 2.0: it has the API of 2.0 that 1.x can get, and deprecates
what 2.0 replaces. GrumPHP runs with 1.7 as is, but triggers two deprecations:

• new Repository() with an array of options: the working directory is now its second argument,
  and a CliDriver configures git, with the logger;
• Diff::setRepository(): Diff::parse() takes the repository.

This PR fixes both. Without deprecations with 1.7, GrumPHP runs with 2.0 with the same code: a
^1.7 || ^2.0 constraint will be enough, without branching on the version of gitlib.

CliDriver has no counterpart for inherit_environment_variables: Symfony Process makes git
inherit the environment variables anyway. git still gets the variables of the environment
configuration (Dotenv sets them in $_ENV and $_SERVER) and the PATH GrumPHP prepends to;
it no longer gets the entries of $_SERVER that aren't environment variables (PHP_SELF,
SCRIPT_NAME...).

GitRepository takes the CliDriver instead of the array of options, and passes it to
GitRepositoryLocator::locate(). The container builds both.

Tested in a repository with git:pre-commit (stashing the unstaged changes), run, and a diff on
stdin: no deprecation anymore, two before.

[veewee]

@lyrixx Looks good.

So do I understand it correctly that I should tag this one and then later on the 2.x support? Or how do you see this?

[lyrixx]

So do I understand it correctly that I should tag this one and then later on the 2.x support? Or how do you see this?

I think it's a good idea 👍🏼

After, there is no rush to upgrade to gitlib 2.0