users/4851: Convert a full path to a path relative to a directory.

1 files changed, 28 insertions, 0 deletions

diff --git a/Functions/Misc/relative b/Functions/Misc/relative
new file mode 100644
index 000000000..f649e51e7
--- /dev/null
+++ b/Functions/Misc/relative
@@ -0,0 +1,28 @@
+# Print the a relative path from the second directory to the first,
+# defaulting the second directory to $PWD if none is specified.
+emulate -L zsh || return 1
+
+[[ $1 != /* ]] && print $1 && return
+[[ -f $1 ]] && 3=$1:t 1=$1:h
+[[ -d $1 && -d ${2:=$PWD} ]] || return 1
+[[ $1 -ef $2 ]] && print ${3:-.} && return
+
+# The simplest way to eliminate symlinks and ./ and ../ in the paths:
+1=$(cd $1; pwd -r)
+2=$(cd $2; pwd -r)
+
+local -a cur abs
+cur=(${(s:/:)2})	# Split 'current' directory into cur
+abs=(${(s:/:)1} $3)	# Split target directory into abs
+
+# Compute the length of the common prefix, or discover a subdiretory:
+integer i=1
+while [[ i -le $#abs && $abs[i] == $cur[i] ]]
+do
+    ((++i > $#cur)) && print ${(j:/:)abs[i,-1]} && return
+done
+
+2=${(j:/:)cur[i,-1]/*/..}	# Up to the common prefix directory and
+1=${(j:/:)abs[i,-1]}		# down to the target directory or file
+
+print $2${1:+/$1}