add 'mtime' option

docs/configuration.rst

@@ -945,6 +945,16 @@ Description Enable/Disable this downloader module.
 =========== =====
 
 
+downloader.*.mtime
+------------------
+=========== =====
+Type        ``bool``
+Default     ``true``
+Description Use |Last-Modified|_ HTTP response headers
+            to set file modification times.
+=========== =====
+
+
 downloader.*.part
 -----------------
 =========== =====
@@ -1589,6 +1599,7 @@ Description An object with the ``name`` of a post-processor and its options.
 .. |webbrowser.open()| replace:: ``webbrowser.open()``
 .. |datetime.max| replace:: ``datetime.max``
 .. |Path| replace:: ``Path``
+.. |Last-Modified| replace:: ``Last-Modified``
 .. |Logging Configuration| replace:: ``Logging Configuration``
 .. |Postprocessor Configuration| replace:: ``Postprocessor Configuration``
 .. |strptime| replace:: strftime() and strptime() Behavior
@@ -1604,6 +1615,7 @@ Description An object with the ``name`` of a post-processor and its options.
 .. _requests.request(): https://docs.python-requests.org/en/master/api/#requests.request
 .. _timeout:           https://docs.python-requests.org/en/latest/user/advanced/#timeouts
 .. _verify:            https://docs.python-requests.org/en/master/user/advanced/#ssl-cert-verification
+.. _Last-Modified:     https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.29
 .. _`Requests' proxy documentation`: http://docs.python-requests.org/en/master/user/advanced/#proxies
 .. _format string:     https://docs.python.org/3/library/string.html#formatstrings
 .. _format strings:    https://docs.python.org/3/library/string.html#formatstrings

docs/gallery-dl.conf

@@ -152,6 +152,17 @@
 
         "http":
         {
+            "mtime": true,
+            "rate": null,
+            "retries": 5,
+            "timeout": 30.0,
+            "verify": true
+        },
+
+        "ytdl":
+        {
+            "format": null,
+            "mtime": true,
             "rate": null,
             "retries": 5,
             "timeout": 30.0,

gallery_dl/downloader/http.py

@@ -25,6 +25,7 @@ class HttpDownloader(DownloaderBase):
         self.retries = self.config("retries", extractor._retries)
         self.timeout = self.config("timeout", extractor._timeout)
         self.verify = self.config("verify", extractor._verify)
+        self.mtime = self.config("mtime", True)
         self.rate = self.config("rate")
         self.downloading = False
         self.chunk_size = 16384
@@ -151,9 +152,10 @@ class HttpDownloader(DownloaderBase):
         self.downloading = False
         if adj_ext:
             pathfmt.set_extension(adj_ext)
-        filetime = response.headers.get("Last-Modified")
-        if filetime:
-            pathfmt.keywords["_filetime"] = filetime
+        if self.mtime:
+            filetime = response.headers.get("Last-Modified")
+            if filetime:
+                pathfmt.keywords["_filetime"] = filetime
         return True
 
     def receive(self, response, file):

gallery_dl/downloader/ytdl.py

@@ -27,6 +27,7 @@ class YoutubeDLDownloader(DownloaderBase):
             "socket_timeout": self.config("timeout", extractor._timeout),
             "nocheckcertificate": not self.config("verify", extractor._verify),
             "nopart": not self.part,
+            "updatetime": self.config("mtime", True),
         }
         options.update(self.config("raw-options") or {})
 

gallery_dl/option.py

@@ -182,6 +182,12 @@ def build_parser():
         dest="part", nargs=0, action=ConfigConstAction, const=False,
         help="Do not use .part files",
     )
+    downloader.add_argument(
+        "--no-mtime",
+        dest="mtime", nargs=0, action=ConfigConstAction, const=False,
+        help=("Do not set file modification times according to "
+              "Last-Modified HTTP response headers")
+    )
     downloader.add_argument(
         "--no-check-certificate",
         dest="verify", nargs=0, action=ConfigConstAction, const=False,