only rewrite utility files if contents changed

scripts/completion_bash.py

@@ -48,7 +48,7 @@ for action in option.build_parser()._actions:
             opts.append(opt)
 
 PATH = util.path("data/completion/gallery-dl")
-with open(PATH, "w", encoding="utf-8") as file:
+with util.lazy(PATH) as file:
     file.write(TEMPLATE % {
         "opts"    : " ".join(opts),
         "diropts" : "|".join(diropts),

scripts/completion_fish.py

@@ -41,5 +41,5 @@ for action in option.build_parser()._actions:
     opts.append(opt)
 
 PATH = util.path("data/completion/gallery-dl.fish")
-with open(PATH, "w", encoding="utf-8") as file:
+with util.lazy(PATH) as file:
     file.write(TEMPLATE % {"opts": "\n".join(opts)})

scripts/completion_zsh.py

@@ -46,5 +46,5 @@ for action in option.build_parser()._actions:
 
 
 PATH = util.path("data/completion/_gallery-dl")
-with open(PATH, "w", encoding="utf-8") as file:
+with util.lazy(PATH) as file:
     file.write(TEMPLATE % {"opts": " \\\n".join(opts)})

scripts/man.py

@@ -100,7 +100,7 @@ and https://github.com/mikf/gallery-dl/graphs/contributors
 
     if not path:
         path = util.path("data/man/gallery-dl.1")
-    with open(path, "w", encoding="utf-8") as file:
+    with util.lazy(path) as file:
         file.write(TEMPLATE.lstrip() % {
             "options": "\n".join(options),
             "version": gallery_dl.version.__version__,
@@ -218,7 +218,7 @@ and https://github.com/mikf/gallery-dl/graphs/contributors
 
     if not path:
         path = util.path("data/man/gallery-dl.conf.5")
-    with open(path, "w", encoding="utf-8") as file:
+    with util.lazy(path) as file:
         file.write(TEMPLATE.lstrip() % {
             "options": "\n".join(content),
             "version": gallery_dl.version.__version__,

scripts/options.py

@@ -33,10 +33,10 @@ opts = re.sub(r"(?m)^(\w+.*)", "## \\1", opts)  # group names to headings
 opts = opts.replace("\n  ", "\n    ")  # indent by 4
 
 
-outfile = sys.argv[1] if len(sys.argv) > 1 else util.path("docs", "options.md")
-with open(outfile, "w", encoding="utf-8") as fp:
-
-    fp.write(TEMPLATE.format(
+PATH = (sys.argv[1] if len(sys.argv) > 1 else
+        util.path("docs", "options.md"))
+with util.lazy(PATH) as file:
+    file.write(TEMPLATE.format(
         "/".join(os.path.normpath(__file__).split(os.sep)[-2:]),
         opts,
     ))

scripts/supportedsites.py

@@ -1,6 +1,10 @@
 #!/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 a Markdown document listing all supported sites"""
 
 import os
@@ -511,6 +515,7 @@ Consider all sites to be NSFW unless otherwise known.
 
 
 categories, domains = build_extractor_list()
-outfile = sys.argv[1] if len(sys.argv) > 1 else "supportedsites.md"
-with open(util.path("docs", outfile), "w") as fp:
-    fp.write(generate_output(COLUMNS, categories, domains))
+PATH = (sys.argv[1] if len(sys.argv) > 1 else
+        util.path("docs", "supportedsites.md"))
+with util.lazy(PATH) as file:
+    file.write(generate_output(COLUMNS, categories, domains))

scripts/util.py

@@ -1,7 +1,12 @@
 # -*- 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.
+
+import os
+import io
 import sys
-import os.path
 
 ROOTDIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 sys.path.insert(0, os.path.realpath(ROOTDIR))
@@ -11,3 +16,32 @@ def path(*segments, join=os.path.join):
     result = join(ROOTDIR, *segments)
     os.makedirs(os.path.dirname(result), exist_ok=True)
     return result
+
+
+class lazy():
+
+    def __init__(self, path):
+        self.path = path
+        self.buffer = io.StringIO()
+
+    def __enter__(self):
+        return self.buffer
+
+    def __exit__(self, exc, value, tb):
+        # get content of old file
+        try:
+            with open(self.path, encoding="utf-8") as fp:
+                old = fp.read()
+        except Exception:
+            old = None
+
+        # get new content
+        new = self.buffer.getvalue()
+
+        if new != old:
+            # rewrite entire file
+            with open(self.path, "w", encoding="utf-8") as fp:
+                fp.write(new)
+        else:
+            # only update atime and mtime
+            os.utime(self.path)