Make it possible to use "~" or "~user" in the installer.

I've looked for a while, and it seems that there is no easy way to do
this, not even in bash, and worse with /bin/sh.  So this is kind of
resorting to a simple parsing of the input, and using `eval' if it
starts with a tilde.  Note the hack of not doing that when there is a
space, otherwise the `eval' thing will silently ignore it.

This hack means that it's easy to get into a mess if quotes are used
after a tilde, but that was already the case with the use of `eval' to
handle environment variables.  It's not a real security issue, however,
since we're talking about a user who can just run any command anyway.

Also including a test file for the expansion functionality.  If anyone
wants to improve this code, making the tests pass would reveal the
tricky issues.

[FWIW, I've asked on the #bash channel, and the only serious suggestion
was getting the paths as command-line arguments.  This will, however,
defeat the point of being newbie friendly...]

Closes PR 12893.
(cherry picked from commit 0814fd5fb5)

collects/meta/build/unix-installer/installer-header

@@ -54,6 +54,22 @@ lookfor mkdir
 lookfor basename
 lookfor dirname
 
+# substitute env vars and tildes
+expand_path_var() {
+  eval "expanded_val=\"\$$1\""
+  first_part="${expanded_val%%/*}"
+  if [ "x$first_part" = "x$expanded_val" ]; then
+    rest_parts=""
+  else
+    rest_parts="/${expanded_val#*/}"
+  fi
+  case "x$first_part" in
+    x*" "* ) ;;
+    x~* ) expanded_val="`eval \"echo $first_part\"`$rest_parts" ;;
+  esac
+  eval "$1=\"$expanded_val\""
+}
+
 # Need this to make new `tail' respect old-style command-line arguments.  Can't
 # use `tail -n #' because some old tails won't know what to do with that.
 _POSIX2_VERSION=199209
@@ -133,11 +149,9 @@ case "x$where" in
   x2     ) where="/usr/local${TARGET1}" ;;
   x3     ) where="${HOME}${TARGET1}" ;;
   x4 | x. | x./ ) where="`pwd`${TARGET1}" ;;
+  * ) expand_path_var where ;;
 esac
 
-# substitute env vars and tildes
-where="`eval \"echo \\\"$where\\\"\"`"
-
 ###############################################################################
 ## Default system directories prefixed by $1, mimic configure behavior
 ## used for unixstyle targets and for wholedir links
@@ -332,6 +346,7 @@ unixstyle_install() {
     echon "> "; read change_what
     read_dir() {
       echon "New directory (absolute or relative to $where): "; read new_dir
+      expand_path_var new_dir
       case "$new_dir" in
         "/"* ) eval "$1=\"$new_dir\"" ;;
         *    ) eval "$1=\"$where/$new_dir\"" ;;

collects/meta/build/unix-installer/test-expand-path-var

@@ -0,0 +1,47 @@
+#!/bin/sh
+
+awk -- '
+  /^expand_path_var()/ { showing = 1; }
+  { if (showing) print; }
+  /^}/ { showing = 0; }
+' "`dirname \"$0\"/`/installer-header" > "/tmp/test-$$"
+. "/tmp/test-$$"
+rm "/tmp/test-$$"
+
+test() {
+  foo="$1"
+  expand_path_var foo
+  if [ ! "x$foo" = "x$2" ]; then
+    echo "fail: $1 -> $foo; expected $2" 1>&2
+    exit 1
+  fi
+}
+
+test 'blah' "blah"
+test 'blah blah' "blah blah"
+test 'blah  blah' "blah  blah"
+test 'blah=blah' "blah=blah"
+test 'x=1 y=2  z=3' "x=1 y=2  z=3"
+test '$HOME' "$HOME"
+test '$HOME/foo' "$HOME/foo"
+test '$HOME/  foo' "$HOME/  foo"
+test '$HOME  /  foo' "$HOME  /  foo"
+test '~' "$HOME"
+test '~/' "$HOME/"
+test '~/x' "$HOME/x"
+test '~/x/y' "$HOME/x/y"
+test '~/x  /y' "$HOME/x  /y"
+test '~/  x  /  y  ' "$HOME/  x  /  y  "
+test '~/  ' "$HOME/  "
+test '~  ' "~  "
+test '~eli' "$HOME"
+test '~eli ' "~eli "
+test '~e li' "~e li"
+test '~ eli' "~ eli"
+test '~eli /x' "~eli /x"
+test '~root/x' "/root/x"
+test '~bleh' "~bleh"
+test '~bleh ' "~bleh "
+test '~/x  y' "$HOME/x  y"
+test '~/x;pwd' "$HOME/x;pwd"
+echo "All tests passed."