Make Auto-Activation and Projects plugins play nice together (#175)

Activating both auto-activation and projects means that the
virtual environment of the project will be deactivated automatically
when leaving the project directory. This is accomplished by expanding
the Auto-Activation plugin to better detect projects in three steps:

1. Check if currently active virtualenv is connected to a project and
save its path

2. For cases where no activation file exists in the project directory,
additionally check if activation root is in project path to set
new_virtualenv_name

3. Finally, additionally check if any virtualenv is active while project
path doesn't match activation root. If so, auto-deactivate virtualenv

docs/plugins.rst

@@ -136,6 +136,9 @@ directory.
 
     If you are using both the *Compatibility Aliases* and *Projects* plugins,
     ``workon`` will alias ``vf workon`` instead of ``vf activate``.
+    If you are using both the *Auto-activation* and *Projects* plugins, the
+    project's virtual environment will be deactivated automatically when you
+    leave the project's directory.
 
 
 Commands

virtualfish/auto_activation.fish

@@ -6,14 +6,30 @@ function __vfsupport_auto_activate --on-variable PWD
         return
     end
 
-    # find an auto-activation file
+    # find an auto-activation file or determine whether inside a project directory
     set -l activation_root $PWD
     set -l new_virtualenv_name ""
+
+    # Projects plugin compatibility: Enable auto-deactivation (1/3)
+    # Check if active virtualenv (if any) is connected to a project
+    if test -e "$VIRTUAL_ENV/.project"
+        set project_path (command cat "$VIRTUAL_ENV/.project")
+    end
+
     while test $activation_root != ""
         if test -f "$activation_root/$VIRTUALFISH_ACTIVATION_FILE"
             set new_virtualenv_name (command cat "$activation_root/$VIRTUALFISH_ACTIVATION_FILE")
             break
+
+        # Projects plugin compatibility: Enable auto-deactivation (2/3)
+        # vf workon might activate virtualenvs without activation files. To detect those instances
+        # here in the Auto-activation plugin, check if activation root is a project path. If so,
+        # set new_virtualenv_name to the basename of the project path
+        else if test "$project_path" = "$activation_root"
+            set new_virtualenv_name (command basename $project_path)
+            break
         end
+
         # this strips the last path component from the path.
         set activation_root (echo $activation_root | sed 's|/[^/]*$||')
     end
@@ -29,6 +45,12 @@ function __vfsupport_auto_activate --on-variable PWD
         # if there's an auto-activated virtualenv, deactivate it
         if set -q VIRTUAL_ENV VF_AUTO_ACTIVATED
             vf deactivate
+
+        # Projects plugin compatibility: Enable auto-deactivation (3/3)
+        # vf workon doesn't set VF_AUTO_ACTIVATED. To deactivate virtualenv automatically when
+        # leaving project directory, we check if any virtualenv is active while not in project path
+        else if begin set -q VIRTUAL_ENV; and test "$project_path" != "$activation_root"; end
+            vf deactivate
         end
     end
 end