bug#20015: 25.0.50; Slow Emacs startup after recent TRAMP changes

[Stefan Monnier]

> only 3 times, and it is called only when you open a remote file
> (tramp.el is loaded).

Loading tramp.el does not guarantee we want to open a remote file (it
could be a local file via /su: for example).

> I would like to avoid these calls completely, if somebody could tell me
> a robust test for knowing which kind of ControlMaster, ControlPath and
> ControlPersist options are supported by the local ssh stanza. And no, I
> don't want to check the ssh version; this isn't robust.

I like using "" for tramp-ssh-controlmaster-options, FWIW ;-)

FWIW, I find that for OpenSSH on Debian, "ssh -o
<optionname>=<optiovalue>" never waits and gives different outputs
("command-line: line 0: Bad configuration option: <optionname>",
"command-line line 0: unsupported option <optionvalue>", or the help
text).  Not sure if it's robust for other systems and other versions of ssh.


        Stefan