Add "Clear Cache Directory" command

One of the steps to help fixing various kinds of issues is to ask users to
delete the "$DATA/Cache" directory. This commit adds a command to simplify that
step.

Default.sublime-commands

@@ -27,6 +27,10 @@
         "caption": "Package Control: Advanced Upgrade Packages",
         "command": "upgrade_packages"
     },
+    {
+        "caption": "Package Control: Clear Cache Directory",
+        "command": "clear_package_cache"
+    },
     {
         "caption": "Package Control: Create Package File",
         "command": "create_package"

package_control/commands/__init__.py

@@ -1,5 +1,6 @@
 from .add_channel_command import AddChannelCommand
 from .add_repository_command import AddRepositoryCommand
+from .clear_package_cache_command import ClearPackageCacheCommand
 from .create_package_command import CreatePackageCommand
 from .disable_package_command import DisablePackageCommand
 from .disable_packages_command import DisablePackagesCommand
@@ -32,6 +33,7 @@
 __all__ = [
     'AddChannelCommand',
     'AddRepositoryCommand',
+    'ClearPackageCacheCommand',
     'CreatePackageCommand',
     'DisablePackageCommand',
     'DisablePackagesCommand',

package_control/commands/clear_package_cache_command.py

@@ -0,0 +1,32 @@
+import sublime
+import sublime_plugin
+
+from ..clear_directory import clear_directory
+from ..show_error import show_message
+from ..sys_path import cache_path, shortpath
+
+
+class ClearPackageCacheCommand(sublime_plugin.ApplicationCommand):
+
+    """
+    A command that clears out ST's Cache directory.
+    """
+
+    def run(self):
+        folder = cache_path()
+        display_folder = shortpath(folder)
+
+        if not sublime.ok_cancel_dialog(
+            msg='Do you want to clear "{}" to reset all packages ' "to freshly installed state?".format(display_folder),
+            title="Clear Sublime Text Cache Directory?",
+        ):
+            return
+
+        if clear_directory(folder, ignore_errors=False):
+            show_message(
+                """
+                "%s" has been cleared.
+                You might need to restart Sublime Text for changes to take effect.
+                """,
+                display_folder,
+            )

plugin.py

@@ -209,6 +209,7 @@
 
     '.commands.add_channel_command',
     '.commands.add_repository_command',
+    '.commands.clear_package_cache_command',
     '.commands.create_package_command',
     '.commands.disable_package_command',
     '.commands.disable_packages_command',