Provide functions to toggle commandline prefix/suffix

This introduces two functions to
- toggle a process prefix, used for adding "sudo"
- add a job suffix, used for adding "&| less"

Not sure if they are very useful; we'll see.

Closes #7905

share/functions/__fish_paginate.fish

@@ -1,16 +1,8 @@
 function __fish_paginate -d "Paginate the current command using the users default pager"
-
     set -l cmd less
     if set -q PAGER
         echo $PAGER | read -at cmd
     end
 
-    if test -z (commandline -j | string join '')
-        commandline -i $history[1]
-    end
-
-    if commandline -j | not string match -q -r "$cmd *\$"
-        commandline -aj " &| $cmd"
-    end
-
+    fish_commandline_append " &| $cmd"
 end

share/functions/__fish_prepend_sudo.fish

@@ -1,19 +1,3 @@
-function __fish_prepend_sudo -d "Prepend 'sudo ' to the beginning of the current commandline"
-    # If there is no commandline, insert the last item from history
-    # and *then* toggle
-    if not commandline | string length -q
-        commandline -r "$history[1]"
-    end
-
-    set -l cmd (commandline -po)
-    set -l cursor (commandline -C)
-
-    if test "$cmd[1]" != sudo
-        commandline -C 0
-        commandline -i "sudo "
-        commandline -C (math $cursor + 5)
-    else
-        commandline -r (string sub --start=6 (commandline -p))
-        commandline -C -- (math $cursor - 5)
-    end
+function __fish_prepend_sudo -d " DEPRECATED: use fish_commandline_prepend instead. Prepend 'sudo ' to the beginning of the current commandline"
+    fish_commandline_prepend sudo
 end

share/functions/__fish_shared_key_bindings.fish

@@ -98,8 +98,7 @@ function __fish_shared_key_bindings -d "Bindings shared between emacs and vi mod
     bind --preset $argv \ed 'set -l cmd (commandline); if test -z "$cmd"; echo; dirh; commandline -f repaint; else; commandline -f kill-word; end'
     bind --preset $argv \cd delete-or-exit
 
-    # Prepend 'sudo ' to the current commandline
-    bind --preset $argv \es __fish_prepend_sudo
+    bind --preset $argv \es "fish_commandline_prepend sudo"
 
     # Allow reading manpages by pressing F1 (many GUI applications) or Alt+h (like in zsh).
     bind --preset $argv -k f1 __fish_man_page

share/functions/fish_commandline_append.fish

@@ -0,0 +1,15 @@
+function fish_commandline_append --description "Append the given string to the command-line, or remove the suffix if already there"
+    if not commandline | string length -q
+        commandline -r $history[1]
+    end
+
+    set -l escaped (string escape --style=regex -- $argv[1])
+    set -l job (commandline -j | string collect)
+    if set job (string replace -r -- $escaped\$ "" $job)
+        set -l cursor (commandline -C)
+        commandline -rj -- $job
+        commandline -C $cursor
+    else
+        commandline -aj -- $argv[1]
+    end
+end

share/functions/fish_commandline_prepend.fish

@@ -0,0 +1,16 @@
+function fish_commandline_prepend --description "Prepend the given string to the command-line, or remove the prefix if already there"
+    if not commandline | string length -q
+        commandline -r $history[1]
+    end
+
+    set -l escaped (string escape --style=regex -- $argv[1])
+    set -l process (commandline -p | string collect)
+    if set process (string replace -r -- "^$escaped " "" $process)
+        commandline --replace -p -- $process
+    else
+        set -l cursor (commandline -C)
+        commandline -C 0 -p
+        commandline -i -- "$argv[1] "
+        commandline -C (math $cursor + (string length -- "$argv[1] "))
+    end
+end