Merge pull request #719 from sudharsh/go_minver_verify

The required go version to build packer seems to be 1.2

CONTRIBUTING.md

@@ -53,9 +53,8 @@ it raises the chances we can quickly merge or address your contributions.
 If you have never worked with Go before, you will have to complete the
 following steps in order to be able to compile and test Packer.
 
-1. Install Go. On a Mac, you can `brew install go`. Make sure the Go
-   version is at least Go 1.1. Packer will not work with anything less than
-   Go 1.1.
+1. Install Go. Make sure the Go version is at least Go 1.2. Packer will not work with anything less than
+   Go 1.2. On a Mac, you can `brew install go` to install Go 1.2.
 
 2. Set and export the `GOPATH` environment variable. For example, you can
    add `export GOPATH=$HOME/Documents/golang` to your `.bash_profile`.

README.md

@@ -70,7 +70,7 @@ http://www.packer.io/docs
 ## Developing Packer
 
 If you wish to work on Packer itself, you'll first need [Go](http://golang.org)
-installed (version 1.1+ is _required_). Make sure you have Go properly installed,
+installed (version 1.2+ is _required_). Make sure you have Go properly installed,
 including setting up your [GOPATH](http://golang.org/doc/code.html#GOPATH).
 
 For some additional dependencies, Go needs [Mercurial](http://mercurial.selenic.com/)

scripts/devcompile.sh

@@ -8,6 +8,40 @@ OK_COLOR="\x1b[32;01m"
 ERROR_COLOR="\x1b[31;01m"
 WARN_COLOR="\x1b[33;01m"
 
+# http://stackoverflow.com/questions/4023830/bash-how-compare-two-strings-in-version-format
+verify_go () {
+    if [[ $1 == $2 ]]
+    then
+        return 0
+    fi
+    local IFS=.
+    local i ver1=($1) ver2=($2)
+
+    for ((i=${#ver1[@]}; i<${#ver2[@]}; i++))
+    do
+        ver1[i]=0
+    done
+    for ((i=0; i<${#ver1[@]}; i++))
+    do
+        if [[ -z ${ver2[i]} ]]
+        then
+            ver2[i]=0
+        fi
+        if ((10#${ver1[i]} > 10#${ver2[i]}))
+        then
+            echo -e "${ERROR_COLOR}==> Required Go version $1 not installed. Found $2 instead"
+            exit 1
+        fi
+    done
+}
+
+GO_MINIMUM_VERSION=1.2
+GO_INSTALLED_VERSION=$(go version | cut -d ' ' -f 3)
+GO_INSTALLED_VERSION=${GO_INSTALLED_VERSION#"go"}
+
+echo -e "${OK_COLOR}==> Verifying Go"
+verify_go $GO_MINIMUM_VERSION $GO_INSTALLED_VERSION
+
 # Get the parent directory of where this script is.
 SOURCE="${BASH_SOURCE[0]}"
 while [ -h "$SOURCE" ] ; do SOURCE="$(readlink "$SOURCE")"; done