Add a debug flag to know what is happening

Author: eloyesp

doc/man/ruby-install.1.md

@@ -92,6 +92,9 @@ https://github.com/postmodern/ruby-install#readme
 	Downloads the latest ruby versions and checksums from the ruby-versions
 	repository (https://github.com/postmodern/ruby-versions#readme).
 
+`-d`, `--debug`
+	Show each command being run (set -x)
+
 `-V`, `--version`
 	Prints the current ruby-install version.
 

share/man/man1/ruby-install.1

@@ -119,6 +119,10 @@ Downloads the latest ruby versions and checksums from the ruby\-versions
 repository (https:\[sl]\[sl]github\.com\[sl]postmodern\[sl]ruby\-versions\[sh]readme)\.
 .LP
 .TP
+\fB-d\fR, \fB--debug\fR
+Show each command being run (set -x)
+.LP
+.TP
 \fB-V\fR, \fB--version\fR
 Prints the current ruby\-install version\.
 .LP

share/ruby-install/ruby-install.sh

@@ -52,6 +52,7 @@ Options:
 	--no-install-deps	Do not install build dependencies before installing Ruby
 	--no-reinstall  	Skip installation if another Ruby is detected in same location
 	-L, --latest		Downloads the latest ruby versions and checksums
+	-d, --debug		Show each command being run (set -x)
 	-V, --version		Prints the version
 	-h, --help		Prints this message
 
@@ -179,6 +180,10 @@ function parse_options()
 				force_update=1
 				shift
 				;;
+			-d|--debug)
+				set -x
+				shift
+				;;
 			-V|--version)
 				echo "ruby-install: $ruby_install_version"
 				exit