CURLOPT_DEFAULT_PROTOCOL: added

- Add new option CURLOPT_DEFAULT_PROTOCOL to allow specifying a default
protocol for schemeless URLs.

- Add new tool option --proto-default to expose
CURLOPT_DEFAULT_PROTOCOL.

In the case of schemeless URLs libcurl will behave in this way:

When the option is used libcurl will use the supplied default.

When the option is not used, libcurl will follow its usual plan of
guessing from the hostname and falling back to 'http'.

1 files changed, 5 insertions, 3 deletions

diff --git a/docs/libcurl/opts/CURLOPT_URL.3 b/docs/libcurl/opts/CURLOPT_URL.3
index 6e4824a9f..83d41c10b 100644
--- a/docs/libcurl/opts/CURLOPT_URL.3
+++ b/docs/libcurl/opts/CURLOPT_URL.3
@@ -40,9 +40,11 @@ libcurl doesn't validate the syntax or use this variable until the transfer is
 issued. Even if you set a crazy value here, \fIcurl_easy_setopt(3)\fP will
 still return \fICURLE_OK\fP.
 
-If the given URL lacks the scheme (such as "http://" or "ftp://" etc) then
-libcurl will attempt to resolve the protocol based on one of the following
-given host names: HTTP, FTP, DICT, LDAP, IMAP, POP3 or SMTP
+If the given URL is missing a scheme name (such as "http://" or "ftp://" etc)
+then libcurl will make a guess based on the host. If the outermost sub-domain
+name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP then that protocol will be
+used, otherwise HTTP will be used. Since 7.45.0 guessing can be disabled by
+setting a default protocol, see \fICURLOPT_DEFAULT_PROTOCOL(3)\fP for details.
 
 Should the protocol, either that specified by the scheme or deduced by libcurl
 from the host name, not be supported by libcurl then