Re: [Patch 1/3] connect.c: add nonstopssh variant to the sshVariant set.

3 messages, 2 authors, 2021-06-05 · open the first message on its own page

Re: [Patch 1/3] connect.c: add nonstopssh variant to the sshVariant set.

From: Junio C Hamano <hidden>
Date: 2021-06-04 19:51:38

"Randall S. Becker" [off-list ref] writes:
The primary
problem is supplying -S $ZSSH0 on the command line causes $ZSSH0
to be resolved as a shell variable. It is not.
I think we've heard that one before, and the whole thing sounds like
you are saying that a command line

    $ cmd $ZSSH0

expects ZSSH0 to be a variable and tries to interpolate its value
before passing it to "cmd" while you want "cmd" to see a literal
string that begins with a dollar sign.

And the standard solution to that problem obviously is to tell the
shell that the dollar-sign is not a reference to a variable by
quoting, by using any variant of e.g.

    $ cmd \$ZSSH0
    $ cmd '$ZSSH0'
    $ cmd "\$ZSSH0"

As far as I can tell, the code in connect.c that spawns ssh via
GIT_SSH_COMMAND uses the pretty vanilla run_command() interface,
and that ought to be capable of producing such a command line, so I
am lost as to where the need to have special case comes from.

"cmd" here may be "ssh" but run_command() should not care what exact
command is being invoked.  I am puzzled why a simple quoting like
the following cannot be adjusted for this particular case, for
example:

    $ cat >>.git/config <<\EOF
    [alias]
	cmdtest0 = "!echo ..\\$ZSSH0.."
	cmdtest1 = "!echo ..$ZSSH0.."
    EOF
    $ ZSSH0=foo git cmdtest0
    ..$ZSSH0..
    $ ZSSH0=foo git cmdtest1
    ..foo..

RE: [Patch 1/3] connect.c: add nonstopssh variant to the sshVariant set.

From: Randall S. Becker <hidden>
Date: 2021-06-04 20:35:35

On June 4, 2021 3:52 PM, Junio C Hamano wrote:
"Randall S. Becker" [off-list ref] writes:
quoted
The primary
problem is supplying -S $ZSSH0 on the command line causes $ZSSH0 to be
resolved as a shell variable. It is not.
I think we've heard that one before, and the whole thing sounds like you are saying that a command line

   $ cmd $ZSSH0

expects ZSSH0 to be a variable and tries to interpolate its value before passing it to "cmd" while you want "cmd" to see a literal
string that
begins with a dollar sign.

And the standard solution to that problem obviously is to tell the shell that the dollar-sign is not a reference to a variable by
quoting, by
using any variant of e.g.

   $ cmd \$ZSSH0
   $ cmd '$ZSSH0'
   $ cmd "\$ZSSH0"
I'm going to have to retest this, but, when I last tried this, admittedly around git 2.0, what happened was that one level of
escaping the $ worked for ls-remote, but we needed two levels for upload-pack which seemed to have two shells processing the
command. I might be wrong about the specifics (been 4 years), but there was an inconsistency with the number of required escapes.
The single quote did not work for upload-pack at the time. It is entirely possible that the second level indirection happened
because the execution of the sshoss command itself cross over a platform boundary between the POSIX and non-POSIX file systems (it
lives in the non-POSIX side).
As far as I can tell, the code in connect.c that spawns ssh via GIT_SSH_COMMAND uses the pretty vanilla run_command() interface,
and
that ought to be capable of producing such a command line, so I am lost as to where the need to have special case comes from.
"cmd" here may be "ssh" but run_command() should not care what exact command is being invoked.  I am puzzled why a simple quoting
like the following cannot be adjusted for this particular case, for
example:

   $ cat >>.git/config <<\EOF
   [alias]
cmdtest0 = "!echo ..\\$ZSSH0.."
cmdtest1 = "!echo ..$ZSSH0.."
   EOF
   $ ZSSH0=foo git cmdtest0
   ..$ZSSH0..
   $ ZSSH0=foo git cmdtest1
   ..foo..
The multi-level resolution that I experienced is not covered in this situation. Still going to investigate this. I'm working on a
different approach to extend my wrapper script to parse out the port, to supply to sshoss, which is not complaint with the standard
ssh. If I have to stick with that script, there's no point going further on this variant.

RE: [Patch 1/3] connect.c: add nonstopssh variant to the sshVariant set.

From: Randall S. Becker <hidden>
Date: 2021-06-05 21:57:01

On June 4, 2021 4:35 PM, I wrote:
To: 'Junio C Hamano' <redacted>
Cc: 'Git Mailing List' <redacted>
Subject: RE: [Patch 1/3] connect.c: add nonstopssh variant to the sshVariant set.

On June 4, 2021 3:52 PM, Junio C Hamano wrote:
quoted
"Randall S. Becker" [off-list ref] writes:
quoted
The primary
problem is supplying -S $ZSSH0 on the command line causes $ZSSH0 to
be resolved as a shell variable. It is not.
I think we've heard that one before, and the whole thing sounds like
you are saying that a command line

   $ cmd $ZSSH0

expects ZSSH0 to be a variable and tries to interpolate its value
before passing it to "cmd" while you want "cmd" to see a literal string that begins with a dollar sign.

And the standard solution to that problem obviously is to tell the
shell that the dollar-sign is not a reference to a variable by quoting, by using any variant of e.g.

   $ cmd \$ZSSH0
   $ cmd '$ZSSH0'
   $ cmd "\$ZSSH0"
I'm going to have to retest this, but, when I last tried this, admittedly around git 2.0, what happened was that one level of
escaping the $
worked for ls-remote, but we needed two levels for upload-pack which seemed to have two shells processing the command. I might be
wrong about the specifics (been 4 years), but there was an inconsistency with the number of required escapes. The single quote did
not
work for upload-pack at the time. It is entirely possible that the second level indirection happened because the execution of the
sshoss
command itself cross over a platform boundary between the POSIX and non-POSIX file systems (it lives in the non-POSIX side).
quoted
As far as I can tell, the code in connect.c that spawns ssh via
GIT_SSH_COMMAND uses the pretty vanilla run_command() interface, and that ought to be capable of producing such a command line,
so I am lost as to where the need to have special case comes from.
quoted
"cmd" here may be "ssh" but run_command() should not care what exact
command is being invoked.  I am puzzled why a simple quoting like the
following cannot be adjusted for this particular case, for
example:

   $ cat >>.git/config <<\EOF
   [alias]
cmdtest0 = "!echo ..\\$ZSSH0.."
cmdtest1 = "!echo ..$ZSSH0.."
   EOF
   $ ZSSH0=foo git cmdtest0
   ..$ZSSH0..
   $ ZSSH0=foo git cmdtest1
   ..foo..
The multi-level resolution that I experienced is not covered in this situation. Still going to investigate this. I'm working on a
different
approach to extend my wrapper script to parse out the port, to supply to sshoss, which is not complaint with the standard ssh. If I
have to
stick with that script, there's no point going further on this variant.
Without a variant (when simple is used), obviously ports cannot be specified. When using the following URL:

    git clone ssh://git@bitbucket.org:22/myproj/repo.git repo

The arguments appended using the auto-detected ssh variant that end up being passed to the GIT_SSH_COMMAND command string are:

    -o SendEnv=GIT_PROTOCOL -p 22 git@bitbucket.org git-upload-pack '/myproj/repo.git'

which is part of the way there, but the -o SendEnv=GIT_PROTOCOL is OpenSSH specific. There is no such argument for the SSHOSS
program. This becomes somewhat problematic.

Of course, a sufficiently smart wrapper can detect this and strip off the -o SendEnv, which I have working. This just does not seem
like a general solution, leading me back down the nonstopssh variant path.

Sigh.

Randall
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