From: Mark Wooding <mdw@distorted.org.uk>
Date: Fri, 2 Aug 2019 19:38:05 +0000 (+0100)
Subject: dot/shell-rc: Colourize `diff' output similarly to `grep'.
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/profile/commitdiff_plain/049cd0157dcb6204cc0f90b7c54dd1b10de34566?ds=sidebyside

dot/shell-rc: Colourize `diff' output similarly to `grep'.

There's a problem here because of a `zsh' bug:

	$ diff -u <(thing) <(thong) | blah
	diff: /proc/self/fd/13: No such file or directory
	diff: /proc/self/fd/14: No such file or directory

caused by the process-substitution pipes being lost somewhere.

Work around this as (a)

	$ diff -u =(thing) =(thong) | blah

(produces temporary files), or (b)

	$ { diff -u <(thing) <(thong) } | blah

(extra typing).
---

diff --git a/dot/shell-rc b/dot/shell-rc
index 965e8ab..aad0918 100644
--- a/dot/shell-rc
+++ b/dot/shell-rc
@@ -163,6 +163,21 @@ alias egrep="greplike egrep"
 alias fgrep="greplike fgrep"
 alias zgrep="greplike zgrep"
 
+## Arrange for `diff' output to be in colour.
+export DIFF_COLORS="hd=1:ln=36:ad=32:de=31"
+difflike () {
+  local diff=$1; shift
+  if [ -t 1 ]; then
+    command $diff \
+	    ${DIFF_COLORS+--color=always} \
+	    ${DIFF_COLORS+--palette="$DIFF_COLORS"} \
+	    "$@" | mdw-pager
+  else
+    command $diff "$@" | cat
+  fi
+}
+alias diff="difflike diff"
+
 ###--------------------------------------------------------------------------
 ### Other hacks.