New HOMELY_PULL_WHEN_DIRTY override

docs/ref/cli.rst

@@ -60,6 +60,12 @@ Performs a ``git pull`` in each of the repositories registered with `homely
 add`_, runs all of their ``HOMELY.py`` scripts, and then performs
 :any:`automatic cleanup <automatic_cleanup>` as necessary.
 
+If `HOMELY_PULL_WHEN_DIRTY=1` is present in the environment, then homely will attempt to use `git
+pull` in the registered repositories even if they have uncommitted changes. This behaviour will
+eventually become the default. You can avoid merge conflicts from pulls in your repositories by
+running `git config pull.ff only` in each of your repositories, of using `git config --global
+pull.ff only` to set this option globally.
+
 ``homely update [OPTIONS] [REPO ...]``
 
 ``REPO``

homely/_ui.py

@@ -140,6 +140,8 @@ def run_update(infos, pullfirst, only=None, cancleanup=None, quick=None):
         if os.path.exists(FAILFILE):
             os.unlink(FAILFILE)
 
+    must_abort_when_dirty = os.getenv("HOMELY_PULL_WHEN_DIRTY", "0") != "1"
+
     try:
         # write the section file with the current section name
         _write(SECTIONFILE, "<preparing>")
@@ -157,8 +159,9 @@ def run_update(infos, pullfirst, only=None, cancleanup=None, quick=None):
                 if pullfirst:
                     with note("Pulling changes for {}".format(
                             localrepo.repo_path)):
-                        if localrepo.isdirty():
+                        if must_abort_when_dirty and localrepo.isdirty():
                             dirty("Aborting - uncommitted changes")
+                            dirty("(use HOMELY_PULL_WHEN_DIRTY=1 to override)")
                         else:
                             try:
                                 localrepo.pullchanges()