add fish shell completion

Makefile

@@ -24,7 +24,7 @@ test:
 executable:
 	scripts/pyinstaller.py
 
-completion: data/completion/gallery-dl data/completion/_gallery-dl
+completion: data/completion/gallery-dl data/completion/_gallery-dl data/completion/gallery-dl.fish
 
 man: data/man/gallery-dl.1 data/man/gallery-dl.conf.5
 
@@ -46,3 +46,6 @@ data/completion/gallery-dl: gallery_dl/option.py scripts/completion_bash.py
 
 data/completion/_gallery-dl: gallery_dl/option.py scripts/completion_zsh.py
 	$(PYTHON) scripts/completion_zsh.py
+
+data/completion/gallery-dl.fish: gallery_dl/option.py scripts/completion_fish.py
+	$(PYTHON) scripts/completion_fish.py

scripts/completion_fish.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Generate fish completion script from gallery-dl's argument parser"""
+
+import util
+from gallery_dl import option
+
+
+TEMPLATE = """complete -c gallery-dl -x
+%(opts)s
+"""
+
+opts = []
+for action in option.build_parser()._actions:
+    if not action.option_strings:
+        continue
+
+    opt = "complete -c gallery-dl"
+
+    if action.metavar:
+        if action.metavar == "FILE":
+            opt += " -r -F"
+        elif action.metavar == "PATH":
+            opt += " -x -a '(__fish_complete_directories)'"
+        else:
+            opt += " -x"
+
+    if len(action.option_strings) == 1:
+        opt += " -l '" + action.option_strings[0].replace("--", "", 1) + "'"
+    else:
+        opt += " -s '" + action.option_strings[0].replace(
+            "-", "", 1) + "' -l '" + action.option_strings[1].replace(
+                "--", "", 1) + "'"
+
+    opt += " -d '" + action.help.replace("'", '"') + "'"
+
+    opts.append(opt)
+
+PATH = util.path("data/completion/gallery-dl.fish")
+with open(PATH, "w", encoding="utf-8") as file:
+    file.write(TEMPLATE % {"opts": "\n".join(opts)})

setup.py

@@ -35,6 +35,7 @@ def check_file(fname):
     for (path, files) in [
         ("share/bash-completion/completions", ["data/completion/gallery-dl"]),
         ("share/zsh/site-functions"         , ["data/completion/_gallery-dl"]),
+        ("share/fish/vendor_completions.d"  , ["data/completion/gallery-dl.fish"]),
         ("share/man/man1"                   , ["data/man/gallery-dl.1"]),
         ("share/man/man5"                   , ["data/man/gallery-dl.conf.5"]),
     ]