Switch off compression by default

Gzip compression has a number of bugs which need to be ironed out before
we can support it by default. Some of these stem from a misunderstanding
of the HTTP spec, but a lot of them are also due to many web servers not
being compliant with RFC 7231.

With this commit, I am marking GZip compression support as experimental
in GNU Wget pending further investigation and the addition of tests.

* src/init.c (defaults): Switch of compression support by default
* docs/wget.texi: State that compression is experimental

doc/wget.texi

@@ -1543,10 +1543,13 @@ If @samp{auto} or @samp{gzip} are specified, Wget asks the server to
 compress the file using the gzip compression format. If the server
 compresses the file and responds with the @code{Content-Encoding}
 header field set appropriately, the file will be decompressed
-automatically. This is the default.
+automatically.
 
 If @samp{none} is specified, wget will not ask the server to compress
-the file and will not decompress any server responses.
+the file and will not decompress any server responses. This is the default.
+
+Compression support is currently experimental. In case it is turned on,
+please report any bugs to @code{bug-wget@gnu.org}.
 
 @cindex redirect
 @item --max-redirect=@var{number}

src/init.c

@@ -451,7 +451,7 @@ defaults (void)
 #endif
 
 #ifdef HAVE_LIBZ
-  opt.compression = compression_auto;
+  opt.compression = compression_none;
 #endif
 
   /* The default for file name restriction defaults to the OS type. */

src/main.c

@@ -777,7 +777,7 @@ HTTP options:\n"),
        --header=STRING             insert STRING among the headers\n"),
 #ifdef HAVE_LIBZ
     N_("\
-       --compression=TYPE          choose compression, one of auto, gzip and none\n"),
+       --compression=TYPE          choose compression, one of auto, gzip and none. (default: none)\n"),
 #endif
     N_("\
        --max-redirect              maximum redirections allowed per page\n"),