More work in git module

Rename pull() to fetch().  It does a git fetch and then a
git fetch --tags.
Add _run() method to handle all subprocess.Popen calls.  Change
all previous calls to subprocess.Popen to use _run().

library/git

@@ -63,6 +63,12 @@ examples:
 import re
 import tempfile
 
+def _run(args):
+    cmd = subprocess.Popen(args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    out, err = cmd.communicate()
+    rc = cmd.returncode
+    return (rc, out, err)
+
 def get_version(dest):
     ''' samples the version of the git repo '''
     os.chdir(dest)
@@ -77,12 +83,7 @@ def clone(repo, dest):
         os.makedirs(os.path.dirname(dest))
     except:
         pass
-    cmd = "git clone %s %s" % (repo, dest)
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=tempfile.gettempdir())
-    (out, err) = cmd.communicate()
-    rc = cmd.returncode
-    return (rc, out, err)
-
+    return _run("git clone %s %s" % (repo, dest))
 
 def has_local_mods(dest):
     os.chdir(dest)
@@ -100,19 +101,13 @@ def reset(module,dest,force):
     os.chdir(dest)
     if not force and has_local_mods(dest):
         module.fail_json(msg="Local modifications exist in repository (force=no).")
-    cmd = "git reset --hard HEAD"
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    (out, err) = cmd.communicate()
-    rc = cmd.returncode
-    return (rc, out, err)
+    return _run("git reset --hard HEAD")
 
 def get_branches(module, dest):
     os.chdir(dest)
     branches = []
-    cmd = "git branch -a"
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    out, err = cmd.communicate()
-    if cmd.returncode != 0:
+    (rc, out, err) = _run("git branch -a")
+    if rc != 0:
         module.fail_json(msg="Could not determine branch data - received %s" % out)
     for line in out.split('\n'):
         branches.append(line.strip())
@@ -156,39 +151,25 @@ def is_not_a_branch(module, dest):
 def get_head_branch(module, dest, remote):
     os.chdir(dest)
     head = ''
-    cmd = "git remote show %s" % remote
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    out, err = cmd.communicate()
-    if cmd.returncode != 0:
+    (rc, out, err) = _run("git remote show %s" % remote)
+    if rc != 0:
         module.fail_json(msg="Could not determine HEAD branch via git remote show")
     for line in out.split('\n'):
         if 'HEAD branch' in line:
             head = line.split()[-1].strip()
     return head
 
-def pull(module, repo, dest, version, remote):
+def fetch(module, repo, dest, version, remote):
     ''' updates repo from remote sources '''
     os.chdir(dest)
-    branches = get_branches(module, dest)
-    cur_branch = ''
-    for b in branches:
-        if b.startswith('* '):
-            cur_branch = b
-    if is_local_branch(module, dest, version) and not is_current_branch(module, dest, version):
-        (rc, out, err) = switch_version(module, dest, remote, version)
+    (rc, out1, err1) = _run("git fetch %s" % remote)
     if rc != 0:
-            module.fail_json(msg=err)
-    if is_not_a_branch(module, dest):
-        head_branch = get_head_branch(module, dest, remote)
-        (rc, out, err) = switch_version(module, dest, remote, head_branch)
-        if rc != 0:
-            module.fail_json(msg=err)
+        module.fail_json(msg="Failed to download remote objects and refs")
 
-    cmd = "git pull -u %s" % remote
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    out, err = cmd.communicate()
-    rc = cmd.returncode
-    return (rc, out, err)
+    (rc, out2, err2) = _run("git fetch --tags %s" % remote)
+    if rc != 0:
+        module.fail_json(msg="Failed to download remote objects and refs")
+    return (rc, out1 + out2, err1 + err2)
 
 def switch_version(module, dest, remote, version):
     ''' once pulled, switch to a particular SHA, tag, or branch '''
@@ -202,10 +183,7 @@ def switch_version(module, dest, remote, version):
     else:
         # is there a better way to do this?
         cmd = "git rebase %s" % remote
-    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    (out, err) = cmd.communicate()
-    rc = cmd.returncode
-    return (rc, out, err)
+    return _run(cmd)
 
 # ===========================================
 
@@ -245,7 +223,7 @@ def main():
         (rc, out, err) = reset(module,dest,force)
         if rc != 0:
             module.fail_json(msg=err)
-        (rc, out, err) = pull(module, repo, dest, version, remote)
+        (rc, out, err) = fetch(module, repo, dest, version, remote)
         if rc != 0:
             module.fail_json(msg=err)