utils: Add 'git_am' helper

We have the same code duplicated in three places and we're going to be
making modifications to it shortly. Drag it out to its own function.

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

git_pw/bundle.py

@@ -3,7 +3,6 @@
 """
 
 import logging
-import subprocess
 import sys
 
 import click
@@ -28,14 +27,7 @@ def apply_cmd(bundle_id, args):
     bundle = api.detail('bundles', bundle_id)
     mbox = api.get(bundle['mbox']).text
 
-    cmd = ['git', 'am']
-    if args:
-        cmd.extend(args)
-    else:
-        cmd.append('-3')
-
-    p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
-    p.communicate(mbox)
+    utils.git_am(mbox, args)
 
 
 @click.command(name='download')

git_pw/patch.py

@@ -3,7 +3,6 @@
 """
 
 import logging
-import subprocess
 import sys
 
 import arrow
@@ -41,14 +40,7 @@ def apply_cmd(patch_id, series, deps, args):
 
     mbox = api.get(patch['mbox'], {'series': series}).content
 
-    cmd = ['git', 'am']
-    if args:
-        cmd.extend(args)
-    else:
-        cmd.append('-3')
-
-    p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
-    p.communicate(mbox)
+    utils.git_am(mbox, args)
 
 
 @click.command(name='download')

git_pw/series.py

@@ -3,7 +3,6 @@
 """
 
 import logging
-import subprocess
 import sys
 
 import arrow
@@ -29,14 +28,7 @@ def apply_cmd(series_id, args):
     series = api.detail('series', series_id)
     mbox = api.get(series['mbox']).text
 
-    cmd = ['git', 'am']
-    if args:
-        cmd.extend(args)
-    else:
-        cmd.append('-3')
-
-    p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
-    p.communicate(mbox)
+    utils.git_am(mbox, args)
 
 
 @click.command(name='download')

git_pw/utils.py

@@ -2,7 +2,23 @@
 Utility functions.
 """
 
+import subprocess
+import sys
+
 
 def trim(string, length=70):  # type: (str, int) -> str
     """Trim a string to the given length."""
     return (string[:length - 1] + '...') if len(string) > length else string
+
+
+def git_am(mbox, args):
+    """Execute git-am on a given mbox file."""
+    cmd = ['git', 'am']
+    if args:
+        cmd.extend(args)
+    else:
+        cmd.append('-3')
+    cmd.append(mbox)
+
+    p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
+    p.communicate(mbox)