Add zuul.project.src_dir variable

For ease of use in writing ad-hoc jobs, include a variable for the
directory on the nodes where the source code will be.

Change-Id: Idb7b3a14766497d7013e054fbe1279cc8809fdb9

doc/source/user/jobs.rst

@@ -202,6 +202,13 @@ of item.
          The full canonical name of the project including hostname.
          E.g., `git.example.com/org/project`.
 
+      .. var:: src_dir
+
+         The path to the source code on the remote host, relative
+         to the home dir of the remote user.
+         E.g., `src/git.example.com/org/project`.
+
+
    .. var:: tenant
 
       The name of the current Zuul tenant.
@@ -243,6 +250,12 @@ of item.
             The full canonical name of the project including hostname.
             E.g., `git.example.com/org/project`.
 
+         .. var:: src_dir
+
+            The path to the source code on the remote host, relative
+            to the home dir of the remote user.
+            E.g., `src/git.example.com/org/project`.
+
       .. var:: branch
 
          The target branch of the change (without the `refs/heads/` prefix).

tests/fixtures/config/ansible/git/common-config/playbooks/check-vars.yaml

@@ -21,6 +21,7 @@
           - zuul.project.name == 'org/project'
           - zuul.project.canonical_hostname == 'review.example.com'
           - zuul.project.canonical_name == 'review.example.com/org/project'
+          - zuul.project.src_dir == 'src/review.example.com/org/project'
 
     - debug:
         msg: "vartest secret {{ vartest_secret }}"

zuul/executor/client.py

@@ -16,6 +16,7 @@ import copy
 import gear
 import json
 import logging
+import os
 import time
 import threading
 from uuid import uuid4
@@ -154,7 +155,9 @@ class ExecutorClient(object):
             name=item.change.project.name,
             short_name=item.change.project.name.split('/')[-1],
             canonical_hostname=item.change.project.canonical_hostname,
-            canonical_name=item.change.project.canonical_name)
+            canonical_name=item.change.project.canonical_name,
+            src_dir=os.path.join('src', item.change.project.canonical_name),
+        )
 
         zuul_params = dict(build=uuid,
                            buildset=item.current_build_set.uuid,
@@ -186,7 +189,9 @@ class ExecutorClient(object):
                 name=i.change.project.name,
                 short_name=i.change.project.name.split('/')[-1],
                 canonical_hostname=i.change.project.canonical_hostname,
-                canonical_name=i.change.project.canonical_name)
+                canonical_name=i.change.project.canonical_name,
+                src_dir=os.path.join('src', i.change.project.canonical_name),
+            )
             if hasattr(i.change, 'number'):
                 d['change'] = str(i.change.number)
             if hasattr(i.change, 'patchset'):