Add hash function for compatibility with sh/bash

CHANGELOG.md

@@ -68,6 +68,7 @@ fish 3.0 is a major release which brings with it both improvements in functional
 - `test` and `[` now support floating point values in numeric comparisons.
 - Autosuggestions try to avoid arguments that are already present in the command line.
 - Variables may be used inside commands (#154).
+- A `hash` function has been added for compatibiility with `sh` and `bash`
 
 ## Other significant changes
 - Command substitution output is now limited to 10 MB by default (#3822).

share/functions/hash.fish

@@ -0,0 +1,10 @@
+# Under (ba)sh, `hash` acts like a caching `which`, but it doesn't print
+# anything on success. Its return code is used to determine success vs failure.
+function hash
+	if not set -q argv[1]
+		echo "Usage: hash FILE" >&2
+		return 1
+	end
+	which $argv[1] 2>/dev/null 1>/dev/null
+	or printf "%s: not found!\n" $argv[1] >&2 && return 2 # ENOENT
+end