installer: extract color sequences definition

tools/install.sh

@@ -1,10 +1,15 @@
-main() {
-  # Use colors, but only if connected to a terminal, and that terminal
-  # supports them.
+#!/bin/sh
+
+# Set up color sequences
+setup_color() {
   if which tput >/dev/null 2>&1; then
-      ncolors=$(tput colors)
+    ncolors=$(tput colors)
+  else
+    ncolors=0
   fi
-  if [ -t 1 ] && [ -n "$ncolors" ] && [ "$ncolors" -ge 8 ]; then
+
+  # Only use colors if connected to a terminal that supports them
+  if [ -t 1 ] && [ $ncolors -ge 8 ]; then
     RED="$(tput setaf 1)"
     GREEN="$(tput setaf 2)"
     YELLOW="$(tput setaf 3)"
@@ -19,6 +24,10 @@ main() {
     BOLD=""
     NORMAL=""
   fi
+}
+
+main() {
+  setup_color
 
   # Only enable exit-on-error after the non-critical colorization stuff,
   # which may fail on systems lacking tput or terminfo