[PATCH] environment: Add a prompt-name argument.

[Roel Janssen]

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:
address@hidden guix]$ guix environment --container --prompt-name="guile" guile
address@hidden ~/sources/guix [guile]#

address@hidden guix]$ guix environment --container -p "guile" guile             
                                      
address@hidden ~/sources/guix [guile]#

address@hidden guix]$ guix environment --container guile
address@hidden ~/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 <address@hidden>
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(-)

diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index 0c69bfc..e36c97e 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -149,6 +149,8 @@ COMMAND or an interactive shell in that environment.\n"))
       --ad-hoc           include all specified packages in the environment 
instead
                          of only their inputs"))
   (display (_ "
+  -p, --prompt-name      use PROMPT-NAME in the command prompt of the 
environment"))
+  (display (_ "
       --pure             unset existing environment variables"))
   (display (_ "
       --search-paths     display needed environment variable definitions"))
@@ -237,6 +239,9 @@ COMMAND or an interactive shell in that environment.\n"))
          (option '(#\N "network") #f #f
                  (lambda (opt name arg result)
                    (alist-cons 'network? #t result)))
+         (option '(#\p "prompt-name") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'prompt-name arg result)))
          (option '("share") #t #f
                  (lambda (opt name arg result)
                    (alist-cons 'file-system-mapping
@@ -376,7 +381,7 @@ environment variables are cleared before setting the new 
ones."
            ((_ . status) status)))))
 
 (define* (launch-environment/container #:key command bash user-mappings
-                                       profile paths network?)
+                                       profile paths network? prompt-name)
   "Run COMMAND within a container that features the software in PROFILE.
 Environment variables are set according to PATHS, a list of native search
 paths.  The global shell is BASH, a file name for a GNU Bash binary in the
@@ -434,7 +439,11 @@ host file systems to mount inside the container."
             (symlink bash "/bin/sh")
 
             ;; Set a reasonable default PS1.
-            (setenv "PS1" "address@hidden \\w [env]\\$ ")
+            (setenv "PS1" (string-append "address@hidden \\w ["
+                                         (if (not prompt-name)
+                                             "env"
+                                             prompt-name)
+                                         "]\\$ "))
 
             ;; Setup directory for temporary files.
             (mkdir-p "/tmp")
@@ -525,13 +534,14 @@ message if any test fails."
 ;; Entry point.
 (define (guix-environment . args)
   (with-error-handling
-    (let* ((opts       (parse-args args))
-           (pure?      (assoc-ref opts 'pure))
-           (container? (assoc-ref opts 'container?))
-           (network?   (assoc-ref opts 'network?))
-           (bootstrap? (assoc-ref opts 'bootstrap?))
-           (system     (assoc-ref opts 'system))
-           (command    (or (assoc-ref opts 'exec)
+    (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))
+           (bootstrap?  (assoc-ref opts 'bootstrap?))
+           (system      (assoc-ref opts 'system))
+           (command     (or (assoc-ref opts 'exec)
                            ;; Spawn a shell if the user didn't specify
                            ;; anything in particular.
                            (if container?
@@ -604,6 +614,7 @@ message if any test fails."
                                                   #:user-mappings mappings
                                                   #:profile profile
                                                   #:paths paths
+                                                  #:prompt-name prompt-name
                                                   #:network? network?)))
                  (else
                   (return
-- 
2.10.0