environment: Add a prompt-name argument.

Dear Guix,

Having multiple virtual terminals open, each running in their own
environment created with @code{guix environment} can become confusing to
the user.  Therefore, I would like to add an option to pass a name to
the shell prompt.  Currently we default to "[env]".

This patch adds a -p and --prompt-name argument to @code{guix
environment}, and puts the argument's value between the square brackets
instead of "env".

Examples:
[roel@hostname guix]$ guix environment --container --prompt-name="guile" guile
roel@hostname ~/sources/guix [guile]#

[roel@hostname guix]$ guix environment --container -p "guile" guile                                                   
roel@hostname ~/sources/guix [guile]#

[roel@hostname guix]$ guix environment --container guile
roel@hostname ~/sources/guix [env]#

Now, I don't know what the correct naming for the argument is
(prompt-name).  So, I have two questions:

0. Do you think we should apply this patch?
1. What name should the argument have?

Kind regards,
Roel Janssen

>From ea958e847019c94a2bde49285f1436dfec72e570 Mon Sep 17 00:00:00 2001
From: Roel Janssen <roel@gnu.org>
Date: Thu, 20 Oct 2016 13:07:15 +0200
Subject: [PATCH] environment: Add a prompt-name argument.

* guix/scripts/environment.scm: Add --prompt-name (-p) argument.
---
 guix/scripts/environment.scm | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

Hi,

Roel Janssen <roel@gnu.org> skribis:

> This patch adds a -p and --prompt-name argument to @code{guix
> environment}, and puts the argument's value between the square brackets
> instead of "env".

Sounds like a good idea!  Maybe ‘--prompt-suffix’ would be more accurate
a name?  WDYT?

>>From ea958e847019c94a2bde49285f1436dfec72e570 Mon Sep 17 00:00:00 2001
> From: Roel Janssen <roel@gnu.org>
> Date: Thu, 20 Oct 2016 13:07:15 +0200
> Subject: [PATCH] environment: Add a prompt-name argument.
>
> * guix/scripts/environment.scm: Add --prompt-name (-p) argument.

Some cosmetic suggestions follow…  :-)

>  (define* (launch-environment/container #:key command bash user-mappings
> -                                       profile paths network?)
> +                                       profile paths network? prompt-name)

Make it

  (prompt-suffix %default-prompt-suffix)

with:

  (define %default-prompt-suffix
    ;; The default prompt suffix
    " [env]")

such that #:prompt-suffix is always a string.

> +            (setenv "PS1" (string-append "\\u@\\h \\w ["
> +                                         (if (not prompt-name)
> +                                             "env"
> +                                             prompt-name)

Assume ‘prompt-name’ is a string.

> +    (let* ((opts        (parse-args args))
> +           (pure?       (assoc-ref opts 'pure))
> +           (container?  (assoc-ref opts 'container?))
> +           (network?    (assoc-ref opts 'network?))
> +           (prompt-name (assoc-ref opts 'prompt-name))

I’d change ‘%default-options’ like this:

  (define %default-options
    `(…
      (prompt-suffix . ,%default-prompt-suffix)))

> +                                                  #:prompt-name prompt-name

Maybe add the brackets here?  Like:

  #:prompt-suffix (match prompt-suffix
                    ("" "")  ;allow for an empty suffix
                    ((? string? suffix) (string-append " [" suffix "]")))

Thanks!

Ludo’.

Ludovic Courtès writes:

> Hi,
>
> Roel Janssen <roel@gnu.org> skribis:
>
>> This patch adds a -p and --prompt-name argument to @code{guix
>> environment}, and puts the argument's value between the square brackets
>> instead of "env".
>
> Sounds like a good idea!  Maybe ‘--prompt-suffix’ would be more accurate
> a name?  WDYT?

I think the goal is to identify the environments by name, and whether
that's by adding a suffix or a prefix doesn't really matter.  So I
believe we should emphasize on "name" and not on "suffix".

I wanted to use --name first, but it doesn't explain why we would use -p
for the short option instead of -n (which is already taken by --dry-run).

WDYT?

>>>From ea958e847019c94a2bde49285f1436dfec72e570 Mon Sep 17 00:00:00 2001
>> From: Roel Janssen <roel@gnu.org>
>> Date: Thu, 20 Oct 2016 13:07:15 +0200
>> Subject: [PATCH] environment: Add a prompt-name argument.
>>
>> * guix/scripts/environment.scm: Add --prompt-name (-p) argument.
>
> Some cosmetic suggestions follow…  :-)
>
>>  (define* (launch-environment/container #:key command bash user-mappings
>> -                                       profile paths network?)
>> +                                       profile paths network? prompt-name)
>
> Make it
>
>   (prompt-suffix %default-prompt-suffix)
>
> with:
>
>   (define %default-prompt-suffix
>     ;; The default prompt suffix
>     " [env]")
>
> such that #:prompt-suffix is always a string.
>
>> +            (setenv "PS1" (string-append "\\u@\\h \\w ["
>> +                                         (if (not prompt-name)
>> +                                             "env"
>> +                                             prompt-name)
>
> Assume ‘prompt-name’ is a string.
>
>> +    (let* ((opts        (parse-args args))
>> +           (pure?       (assoc-ref opts 'pure))
>> +           (container?  (assoc-ref opts 'container?))
>> +           (network?    (assoc-ref opts 'network?))
>> +           (prompt-name (assoc-ref opts 'prompt-name))
>
> I’d change ‘%default-options’ like this:
>
>   (define %default-options
>     `(…
>       (prompt-suffix . ,%default-prompt-suffix)))
>
>> +                                                  #:prompt-name prompt-name
>
> Maybe add the brackets here?  Like:
>
>   #:prompt-suffix (match prompt-suffix
>                     ("" "")  ;allow for an empty suffix
>                     ((? string? suffix) (string-append " [" suffix "]")))
>
> Thanks!
>
> Ludo’.

These are great suggestions!  I will adapt it when we agree
upon the long option name :).

Thanks!

Kind regards,
Roel Janssen

Roel Janssen <roel@gnu.org> skribis:

> Ludovic Courtès writes:
>
>> Hi,
>>
>> Roel Janssen <roel@gnu.org> skribis:
>>
>>> This patch adds a -p and --prompt-name argument to @code{guix
>>> environment}, and puts the argument's value between the square brackets
>>> instead of "env".
>>
>> Sounds like a good idea!  Maybe ‘--prompt-suffix’ would be more accurate
>> a name?  WDYT?
>
> I think the goal is to identify the environments by name, and whether
> that's by adding a suffix or a prefix doesn't really matter.  So I
> believe we should emphasize on "name" and not on "suffix".

Makes sense, that also works for me!

In the code I think it’s still more appropriate to use “suffix” when
we’re talking about the suffix, for clarity.

Thanks,
Ludo’.