Subject: Re: bug#30419: tramp-sh-process-file: effect of tramp-remote-process-environment vs non-top level value of process-environment

From: Noam Postavsky <[email-masked]>
Date: Sun, 11 Feb 2018 09:28:09 -0500

tags 30419 + patch
quit

Michael Albinus <[email-masked]> writes:

> `tramp-remote-process-environment' is still in play. The let-bound
> environment variables from `process-environment' are taken additionally,
> and afterwards. So they would have precedence.
>
> See bug#18940. The major reasoning is, that other packages do not want
> to preload Tramp in order to set `tramp-remote-process-environment',
> even if Tramp isn't used ever.

Thanks, I propose the following patch to the manual to clarify this:

>From 9cafeec6027947e28e3f54ffc7f975a4845227de Mon Sep 17 00:00:00 2001
From: Noam Postavsky <[email-masked]>
Date: Sun, 11 Feb 2018 09:20:29 -0500
Subject: [PATCH v1] Clarify TRAMP process-environment interaction (Bug#30419)

* doc/misc/tramp.texi (Remote processes): Index the
tramp-remote-process-environment description.  Clarify the effects of
let-binding process-environment and the motivation for that behavior.
---
 doc/misc/tramp.texi | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index 25ae8ae3e8..4723547419 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -2596,6 +2596,7 @@ Remote processes
 @end group
 @end lisp
 
+@vindex tramp-remote-process-environment
 Customize user option @option{tramp-remote-process-environment} to
 suit the remote program's environment for the remote host.
 @option{tramp-remote-process-environment} is a list of strings
@@ -2641,11 +2642,13 @@ Remote processes
 @end group
 @end lisp
 
-@value{tramp} does not use the defaults specified in
-@code{process-environment} for running @code{process-file} or
-@code{start-file-process} on remote hosts.  When values from
-@code{process-environment} are needed for remote processes, then set
-them as follows:
+In addition to @option{tramp-remote-process-environment}, you can set
+environment variables for invidivual remote process calls by
+let-binding @code{process-environment}.  @value{tramp} will apply any
+entries which are not present in the global default value of
+@code{process-environment} (overriding
+@option{tramp-remote-process-environment} settings, if they conflict).
+For example:
 
 @lisp
 @group
@@ -2654,8 +2657,10 @@ Remote processes
 @end group
 @end lisp
 
-This works only for environment variables not already set in the
-@code{process-environment}.
+Let-binding in this way works regardless of whether the process to be
+called is local or remote, since @value{tramp} would add just the
+@code{HGPLAIN} setting and local processes would take whole value of
+@code{process-environment} along with the new value of @code{HGPLAIN}.
 
 For integrating other Emacs packages so @value{tramp} can execute
 remotely, please file a bug report.  @xref{Bug Reports}.
-- 
2.11.0