[gareth] Add support for updating the dev env

This commit adds the code which can update the forks
with gareth. It fetches the latest changes in the
upstream and rebases the `master` branch accordingly.

Usage:
```
$ gareth -s sources --update
```

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

gareth/gareth.py

@@ -26,6 +26,7 @@
 """
 
 import os
+import subprocess
 
 import click
 import git.repo.base as grb
@@ -53,6 +54,10 @@
 
 GITHUB_URL = "https://github.com/"
 
+CHECKOUT_MASTER_CMD = ['git', 'checkout', 'master']
+FETCH_UPSTREAM_CMD = ['git', 'fetch', 'upstream']
+REBASE_UPSTREAM_CMD = ['git', 'rebase', 'upstream/master']
+
 
 def source_prompt():
     """Prompt source to read the folder name"""
@@ -172,6 +177,14 @@ def set_upstream(local_repo_path, org, repo):
         click.ClickException(msg)
 
 
+def sync_with_upstream():
+    """Rebase the fork with upstream"""
+
+    subprocess.call(CHECKOUT_MASTER_CMD)
+    subprocess.call(FETCH_UPSTREAM_CMD)
+    subprocess.call(REBASE_UPSTREAM_CMD)
+
+
 def create_dev_setup(token, source):
     """Create the developer setup"""
 
@@ -202,5 +215,28 @@ def create_dev_setup(token, source):
     click.echo("The dev setup is created.")
 
 
+def update_dev_setup(source):
+    """Update the developer setup"""
+
+    click.echo("Updating the developer setup.\n")
+
+    source_path = os.path.join(os.getcwd(), source)
+
+    for repository in REPOS:
+        click.echo("{}...".format(repository))
+
+        org, repo = repository.split('/')
+        dirpath = os.path.join(source_path, repo)
+
+        change_the_directory(dirpath)
+
+        sync_with_upstream()
+
+        click.echo("done\n")
+
+    click.echo()
+    click.echo("The dev setup is updated.")
+
+
 if __name__ == '__main__':
     main()

releases/unreleased/add-support-for-updating-the-dev-environment.yml

@@ -0,0 +1,17 @@
+---
+title: Add support for updating the dev environment
+category: added
+author: Venu Vardhan Reddy Tekula <[email protected]>
+issue: null
+notes: >
+    The support for updating the developer environment
+    is added. This would be needed to update the repos
+    by rebasing the latest changes with the upstream.
+
+    It would open each folder, changes to `master` branch,
+    and rebase the changes with the upstream.
+
+    Usage:
+    ```
+    $ gareth -s sources --update
+    ```