Add an option to kitty.conf to specify a default startup session

Fixes #641

kitty/boss.py

@@ -96,7 +96,7 @@ class Boss:
         )
         set_boss(self)
         self.opts, self.args = opts, args
-        startup_session = create_session(opts, args)
+        startup_session = create_session(opts, args, default_session=opts.startup_session)
         self.keymap = self.opts.keymap.copy()
         if new_os_window_trigger is not None:
             self.keymap.pop(new_os_window_trigger, None)

kitty/config_data.py

@@ -616,6 +616,12 @@ opening new windows, closing windows, reading the content of windows, etc.
 Note that this even works over ssh connections.
 '''))
 
+o('startup_session', 'none', option_type=lambda x: (None if x.lower() == 'none' else x), long_text=_('''
+Path to a session file to use for all kitty instances. Can be overridden
+by using the :option:`--startup-session` command line option for individual
+instances. See :ref:`sessions` in the kitty documentation for details.
+'''))
+
 o('clipboard_control', 'write-clipboard write-primary', option_type=lambda x: frozenset(x.lower().split()), long_text=_('''
 Allow programs running in kitty to read and write from the clipboard. You can
 control exactly which actions are allowed. The set of possible actions is:

kitty/session.py

@@ -7,6 +7,7 @@ import shlex
 from .config_data import to_layout_names
 from .constants import shell_path
 from .layout import all_layouts
+from .utils import log_error
 
 
 class Tab:
@@ -105,10 +106,18 @@ def parse_session(raw, opts):
     return ans
 
 
-def create_session(opts, args=None, special_window=None, cwd_from=None, respect_cwd=False):
+def create_session(opts, args=None, special_window=None, cwd_from=None, respect_cwd=False, default_session=None):
     if args and args.session:
         with open(args.session) as f:
             return parse_session(f.read(), opts)
+    if default_session and default_session != 'none':
+        try:
+            with open(default_session) as f:
+                session_data = f.read()
+        except EnvironmentError:
+            log_error('Failed to read from session file, ignoring: {}'.format(default_session))
+        else:
+            return parse_session(session_data, opts)
     ans = Session()
     current_layout = opts.enabled_layouts[0] if opts.enabled_layouts else 'tall'
     ans.add_tab(opts)