Remove git2go and replace it with go-git

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "static/git2go"]
-	path = static/git2go
-	url = https://github.com/libgit2/git2go.git

README.md

@@ -2,38 +2,6 @@
 
 `git get` - a better way to clone and manage git repositories.
 
-## Build
-
-How to build with `libgit2` statically linked into a single executable without dependencies:
-
-- Install development packages for libssh2 and openssl:
-  ```
-  sudo apt install libssh2-1-dev libssl-dev
-  ```
-
-- Inside the `static` folder there's the `git2go` library added as a submodule (pointing to a correct v30 release). 
-  This, in turn, contains `libgit2` submodule. To ensure the submodules are cloned run:
-  ``` 
-  git submodule update --init --recursive
-  ```
-
-- Build the static `git2go` library:
-  ```
-  cd static/git2go && make install-static
-  ```
-
-- Ensure our `git-get` module uses the static `git2go` library instead of the one downloaded by Go modules by having
-  the following line in `go.mod`:
-  ```
-  replace github.com/libgit2/git2go/v30 => ./static/git2go
-  ```
-
-- Build, install and test `git-get` with `--tags static` flag, eg:
-  ```
-  go build -i --tags static
-  go test --tags static
-  ```
-
 ## Features
 
 Show repo status:

go.mod

@@ -3,10 +3,8 @@ module git-get
 go 1.14
 
 require (
-	github.com/libgit2/git2go/v30 v30.0.3
+	github.com/go-git/go-git/v5 v5.1.0
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/spf13/cobra v1.0.0
 )
-
-replace github.com/libgit2/git2go/v30 => ./static/git2go