ssh: introduce a 'simple' ssh variant

When using the 'ssh' transport, the '-o' option is used to specify an
environment variable which should be set on the remote end.  This allows
git to send additional information when contacting the server,
requesting the use of a different protocol version via the
'GIT_PROTOCOL' environment variable like so: "-o SendEnv=GIT_PROTOCOL".

Unfortunately not all ssh variants support the sending of environment
variables to the remote end.  To account for this, only use the '-o'
option for ssh variants which are OpenSSH compliant.  This is done by
checking that the basename of the ssh command is 'ssh' or the ssh
variant is overridden to be 'ssh' (via the ssh.variant config).

Other options like '-p' and '-P', which are used to specify a specific
port to use, or '-4' and '-6', which are used to indicate that IPV4 or
IPV6 addresses should be used, may also not be supported by all ssh
variants.

Currently if an ssh command's basename wasn't 'plink' or
'tortoiseplink' git assumes that the command is an OpenSSH variant.
Since user configured ssh commands may not be OpenSSH compliant, tighten
this constraint and assume a variant of 'simple' if the basename of the
command doesn't match the variants known to git.  The new ssh variant
'simple' will only have the host and command to execute ([username@]host
command) passed as parameters to the ssh command.

Update the Documentation to better reflect the command-line options sent
to ssh commands based on their variant.

Reported-by: Jeffrey Yasskin <jyasskin@google.com>
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7518ea3af..8bc3f2147 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -518,11 +518,10 @@ other
 	If either of these environment variables is set then 'git fetch'
 	and 'git push' will use the specified command instead of 'ssh'
 	when they need to connect to a remote system.
-	The command will be given exactly two or four arguments: the
-	'username@host' (or just 'host') from the URL and the shell
-	command to execute on that remote system, optionally preceded by
-	`-p` (literally) and the 'port' from the URL when it specifies
-	something other than the default SSH port.
+	The command-line parameters passed to the configured command are
+	determined by the ssh variant.  See `ssh.variant` option in
+	linkgit:git-config[1] for details.
+
 +
 `$GIT_SSH_COMMAND` takes precedence over `$GIT_SSH`, and is interpreted
 by the shell, which allows additional arguments to be included.