From da6937e0cf7055119b76df4b68a560c982cac30e Mon Sep 17 00:00:00 2001
From: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Wed, 7 Nov 2018 19:02:17 -0600
Subject: [PATCH] Extend __fish_complete_suffix to support a virtual $PWD

In writing the completion script for openocd I found the need to
complete paths at the command-line as if they were relative to a
path other than the current $PWD. Given that `$PWD` is currently
global in fish (i.e. no side-effect free `cd` within a subshell)
this is probably good to have for other completions too.

This also fixes a bug in support for explicitly supplying the
description for completions via a `$argv` parameter, which prefixed
the description with `\t` (which is correct) except it did so in
the local scope within an `if` statement, meaning the changes never
had any effect and in the output the description was directly
concatenated to the completions, instead of separated by a tab.
---
 share/functions/__fish_complete_suffix.fish | 28 ++++++++++++++++++---
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/share/functions/__fish_complete_suffix.fish b/share/functions/__fish_complete_suffix.fish
index 6be18ea6e..d7861e953 100644
--- a/share/functions/__fish_complete_suffix.fish
+++ b/share/functions/__fish_complete_suffix.fish
@@ -2,7 +2,8 @@
 # Find files that complete $argv[1], has the suffix $argv[2], and
 # output them as completions with the optional description $argv[3] Both
 # $argv[1] and $argv[3] are optional, if only one is specified, it is
-# assumed to be the argument to complete.
+# assumed to be the argument to complete. If $argv[4] is present, it is
+# treated as a prefix for the path, i.e. in lieu of $PWD.
 #
 
 function __fish_complete_suffix -d "Complete using files"
@@ -13,6 +14,7 @@ function __fish_complete_suffix -d "Complete using files"
     set -l suff
     set -l desc
     set -l files
+    set -l prefix
 
     switch (count $argv)
 
@@ -31,11 +33,24 @@ function __fish_complete_suffix -d "Complete using files"
             set suff $argv[2]
             set desc $argv[3]
 
+        case 4
+            set comp $argv[1]
+            set suff $argv[2]
+            set desc $argv[3]
+            set prefix $argv[4]
+
+            # Only directories are supported as prefixes, and to use the same logic
+            # for both absolute prefixed paths and relative non-prefixed paths, $prefix
+            # must terminate in a `/` if it is present, so it can be unconditionally
+            # prefixed to any path to get the desired result.
+            if not string match -qr '/$' $prefix
+                set prefix $prefix/
+            end
     end
 
     # Strip leading ./ as it confuses the detection of base and suffix
     # It is conditionally re-added below.
-    set base (string replace -r '^("\')?\\./' '' -- $comp | string trim -c '\'"') # " make emacs syntax highlighting happy
+    set base $prefix(string replace -r '^("\')?\\./' '' -- $comp | string trim -c '\'"') # " make emacs syntax highlighting happy
     # echo "base: $base" > /dev/tty
     # echo "suffix: $suff" > /dev/tty
 
@@ -78,8 +93,13 @@ function __fish_complete_suffix -d "Complete using files"
     end
 
     if set -q files[1]
-        if not string match -q -- "$desc" ""
-           set -l desc "\t$desc"
+        if string match -qr -- . "$desc"
+           set desc "\t$desc"
+        end
+        if string match -qr -- . "$prefix"
+            # Ideally, only replace in the beginning of the string, but we have no
+            # way of doing a pcre2 escape so we can use a regex replace instead
+            set files (string replace $prefix "" $files)
         end
         printf "%s$desc\n" $files #| sort -u
     end