[gareth] Add support for creating the dev env

This commit adds the code which automates most of the
setup. It forks all the repos, clones them and sets the
upstream accordingly.

Usage:
```
$ gareth -t xxxx -s sources --create
```

Signed-off-by: Venu Vardhan Reddy Tekula <[email protected]>

gareth/gareth.py

@@ -28,6 +28,9 @@
 import os
 
 import click
+import git.repo.base as grb
+
+from github import Github, BadCredentialsException, GithubException
 
 REPOS = [
     "chaoss/grimoirelab-sirmordred",
@@ -48,6 +51,8 @@
     "chaoss/grimoirelab-manuscripts"
 ]
 
+GITHUB_URL = "https://github.com/"
+
 
 def source_prompt():
     """Prompt source to read the folder name"""
@@ -105,5 +110,97 @@ def main(token, source, operation):
         update_dev_setup(source)
 
 
+def validate_token(token):
+    """Check and validate the GitHub API Token."""
+
+    g = Github(token)
+    try:
+        user = g.get_user()
+        click.echo("Access token is working, {}.\n".format(user.login))
+        return g
+    except BadCredentialsException as ex:
+        msg = "Invalid token.\n"
+        msg += str(ex)
+        raise click.ClickException(msg)
+    except Exception as ex:
+        raise click.ClickException(ex)
+
+
+def change_the_directory(dirpath):
+    """Change the directory"""
+
+    try:
+        os.chdir(dirpath)
+    except Exception as ex:
+        raise click.ClickException(ex)
+
+
+def fork_the_repository(user, repo):
+    """Fork the respository"""
+
+    try:
+        user.create_fork(repo)
+    except GithubException as ex:
+        msg = "Forking aborted.\n"
+        msg += "Please select the appropriate scope (`repo`) for the token.\n"
+        msg += str(ex)
+        raise click.ClickException(msg)
+
+
+def clone_the_repository(user, repo):
+    """Clone the forked repository"""
+
+    try:
+        return grb.Repo.clone_from(
+            GITHUB_URL + user.login + "/" + repo.name + ".git",
+            "{0}/{1}".format(os.getcwd(), repo.name)
+        )
+    except grb.GitCommandError as ex:
+        raise click.ClickException(ex)
+
+
+def set_upstream(local_repo_path, org, repo):
+    """Set upstream to the forked repository"""
+
+    try:
+        grb.Repo.create_remote(
+            local_repo_path, "upstream",
+            GITHUB_URL + org.login + "/" + repo.name + ".git"
+        )
+    except grb.GitCommandError as ex:
+        msg = str(ex)
+        click.ClickException(msg)
+
+
+def create_dev_setup(token, source):
+    """Create the developer setup"""
+
+    g = validate_token(token)
+
+    click.echo("Creating the developer setup.\n")
+
+    user = g.get_user()
+
+    source_path = os.path.join(os.getcwd(), source)
+
+    for repository in REPOS:
+        click.echo("{}...".format(repository), nl=False)
+
+        change_the_directory(source_path)
+
+        org, repo = repository.split('/')
+        org = g.get_organization(org)
+        repo = org.get_repo(repo)
+
+        fork_the_repository(user, repo)
+        local_repo_path = clone_the_repository(user, repo)
+        set_upstream(local_repo_path, org, repo)
+
+        click.echo("done")
+
+    click.echo()
+    click.echo("The dev setup is created.")
+
+
 if __name__ == '__main__':
     main()