Add functionality to create parent directories

This commit introduces an additional option for extended configuration
syntax for linking. It adds the "create" parameter which results in
automatically creating a parent directory if necessary before linking a
file.

README.md

@@ -104,14 +104,19 @@ a trailing "/" character.
 Link commands support an (optional) extended configuration. In this type of
 configuration, instead of specifying source locations directly, targets are
 mapped to extended configuration dictionaries. These dictionaries map "path" to
-the source path, and specify "force" as true if the file or directory should be
-forcibly linked.
+the source path, specify "create" as true if the parent directory should be
+created if necessary, and specify "force" as true if the file or directory
+should be forcibly linked.
 
 ##### Example
 
 ```json
 {
     "link": {
+        "~/.config/terminator": {
+            "path": "config/terminator/",
+            "create": true
+        },
         "~/.vimrc": "vimrc",
         "~/.vim": "vim/",
         "~/.zshrc": {

dotbot/executor/linker.py

@@ -23,6 +23,9 @@ class Linker(Executor):
                 # extended config
                 path = source['path']
                 force = source.get('force', False)
+                create = source.get('create', False)
+                if create:
+                    success &= self._create(destination)
                 if force:
                     success &= self._delete(destination)
             else:
@@ -55,6 +58,19 @@ class Linker(Executor):
         path = os.path.expanduser(path)
         return os.path.exists(path)
 
+    def _create(self, path):
+        success = True
+        parent = os.path.abspath(os.path.join(os.path.expanduser(path), os.pardir))
+        if not self._exists(parent):
+            try:
+                os.makedirs(parent)
+            except OSError:
+                self._log.warning('Failed to create directory %s' % parent)
+                success = False
+            else:
+                self._log.lowinfo('Creating directory %s' % parent)
+        return success
+
     def _delete(self, path):
         success = True
         if self._exists(path) and not self._is_link(path):