[PATCH 0/3] Add support for per-remote and per-namespace SSH options

[Wesley Schwengle <wesleys@opperschaap.net>]

With this changeset applied git is now aware of `sshIdentityFiles' and
`sshOpts'. This allows users to have multiple accounts on the same forges.
A common problem within the developer community. This problem is often
solved by hacking in one's `.ssh/config' and changing hostname URIs to
ensure the correct key is being used.

For years I had zsh wrapper script that was used as the `core.sshCommand' and
is a reference implementation of this change.

In order of importance:

Configuration on the remotes itself. This is easy, straight forward and
should allow people to get it to work quickly:

* `remote.*.sshIdentityFile' and `remote.*.sshOpts'

Configuration set on owner/path style. This is to support `includeIf`
configuration management. For example, a git-forge that host both
employer/client repo's. Eg, `git@gitlab.com/waterkip/git.git' and
`git@gitlab.com/corp/git.git' would have something configured as:

* `core.sshIdentityFile.*', eg

    [core "sshIdentityFile"]
      waterkip = ~/.ssh/id_ed25519_me
      corp     = ~/.ssh/id_ed25519_corporate

And finally, a global override for everything:

* `core.sshIdentityFile' and `core.sshOpts'

I stayed within the `core' namespace, mainly because `core.sshCommand'. I'm
happy to move it to `ssh' or something similar. It would perhaps make
`ssh.*.sshIdentifyFile' more structured, because now that's split between two
core subsections.

The following assumptions have been made to make it safe and sound for
users. When an `sshIdentityFile' is used and no `sshOpts' are configured git
will inject `-F /dev/null' to prevent cycling over all sshIdentityFiles
a user has in their `.ssh/config'. When a user configures `sshOpts', these
take precedence and a user itself is responsible for setting
`-F /dev/null'.

Separate push/pull URIs are not supported by the feature. The biggest problem
with this is that I don't know how to properly configure them with the
namespace constraints. `remote.*.xyz' is as deep as git can go and a push/pull
would require additional configuration. I filed it under edge-case.

There are two new structs introduced: `ssh_options' and `cnx_context'.
They are there to limit the amount of argument passing down the wire. And this
is especially true for `ssh_options' because it keeps `push_ssh_options' dumb.

Wesley Schwengle (3):
  connect: Rename name to command in connect_git()
  connect: Add transport->remote->name to git_connect()
  connect: Add support for per-remote and per-namespace SSH options

 Documentation/config/core.adoc   |  22 ++++
 Documentation/config/remote.adoc |   9 ++
 builtin/fetch-pack.c             |   2 +-
 builtin/send-pack.c              |   2 +-
 connect.c                        | 144 ++++++++++++++++++++--
 connect.h                        |   2 +-
 t/t57xx-ssh-options-config.sh    | 198 +++++++++++++++++++++++++++++++
 transport.c                      |   9 +-
 8 files changed, 375 insertions(+), 13 deletions(-)
 create mode 100755 t/t57xx-ssh-options-config.sh

-- 
2.53.0.722.g8e572876c5