Add support for listing and installing unstable versions

This also adds a big performance boost when loading remote versions.
This is because we switched the versions source from the golang.org
download page to the web UI of the git project hosted at
googlesource.com

https://go.googlesource.com/go/+refs   25 KB   59 ms
https://golang.org/dl/                341 KB  371 ms

This was not the actual reason for the switch, but the fact that the
golang.org download page doesn't list any previuos unstable versions.

CHANGELOG.md

@@ -3,6 +3,7 @@ Changelog
 
 ## Unreleased
 
+- Add support for listing and installing unstable versions
 - Prevent bugs in config files without final newline
 - Ensure the modified PATH is exported on bash and zsh
 - Prevent multiple selection of the same shell in g-install

README.md

@@ -156,6 +156,7 @@ curl -sSL https://git.io/g-install | bash
     -y, --non-interactive   Prevent prompts
     -o, --os                Override operating system
     -a, --arch              Override system architecture
+    -u, --unstable          Include unstable versions in list
 ```
 
 ## Uninstall
@@ -216,7 +217,7 @@ At this point you would have removed `g` and `go` entirely.
     - [x] Add non-interactive mode
     - [x] Warn about installing in an uncommon path. See #5
 - [x] Upgrade script
-- [ ] Add support to select `unstable` versions
+- [x] Add support to select `unstable` versions
 - [x] Install requested version when `g run` cannot find it. See #3
 - [ ] Use better naming for `g install <version>`, maybe `use` or `set`. See #8
 - [x] Improve the --quiet and --non-interactive modifiers

bin/g

@@ -39,6 +39,7 @@ ACTIVATE=true
 QUIET=false
 NO_COLOR=false
 NON_INTERACTIVE=false
+INCLUDE_UNSTABLE=false
 STDIN=
 ARCH=
 OS=
@@ -101,6 +102,7 @@ display_help() {
     -y, --non-interactive   Prevent prompts
     -o, --os                Override operating system
     -a, --arch              Override system architecture
+    -u, --unstable          Include unstable versions in list
 
 EOF
 }
@@ -269,11 +271,20 @@ download() {
 #
 
 get_all_remote_versions() {
-  download 2> /dev/null "https://golang.org/dl/" \
-    | grep -E -o '\"https://dl.google.com/go/go.*\.tar\.gz\"' \
-    | grep -E -o 'go[[:digit:]]+\.[[:digit:]]+(\.[[:digit:]]+)?\b' \
+  local pattern
+
+  if [[ "$INCLUDE_UNSTABLE" = true ]]; then
+    pattern='go[[:digit:]]+(\.[[:alnum:]]+)+\b'
+  else
+    pattern='go[[:digit:]]+(\.[[:digit:]]+)+\b'
+  fi
+
+  download 2> /dev/null "https://go.googlesource.com/go/+refs" \
+    | grep -E -o '\"/go/\+/refs/tags/go.+?\"' \
+    | grep -E -o "$pattern" \
     | tr -d 'go' \
-    | sort -u -k 1,1n -k 2,2n -k 3,3n -t .
+    | sort -k 1,1n -k 2,2n -k 3,3n -t . \
+    | uniq
 }
 
 
@@ -701,6 +712,7 @@ else
       -y|--non-interactive) NON_INTERACTIVE=true;;
       -o|--os) shift; OS=$1;;
       -a|--arch) shift; ARCH=$1;;
+      -u|--unstable) INCLUDE_UNSTABLE=true;;
       --) __cmd_args+=("$@"); break;;
       *) __cmd_args+=("$1");;
     esac