2 files changed, 87 insertions(+), 37 deletions(-)

M README.md
M gover

@@ 8,34 8,44 @@ welcome.
 
 ## Prerequisites
 
-You must have a conventional `PREFIX` directory structure with its `bin`
-directory earlier in your `$PATH` than any other `go` installation.
+`gover` assumes a POSIX environment with `grep`, `sed`, `curl`, and `coreutils`.
 
-Pretty much every linux distro creates this for you at `~/.local`, which is
-the default installation directory. Make sure you update your `$PATH` so
-that `~/.local/bin` is towards the beginning.
+## User install (recommended)
 
-## Install
+Ensure `$HOME/.local/bin` is towards the beginning of your `$PATH`.
 
-Download the script and put it into any `bin` directory that is in your `$PATH`.
-If you're using the default installation prefix, `~/.local/bin` will do.
 
 ```
-curl --tlsv1.2 -o ~/.local/bin/gover https://git.sr.ht/~whereswaldon/gover/blob/main/gover
+curl --tlsv1.2 -o ~/.local/bin/gover https://git.sr.ht/~whereswaldon/gover/blob/main/gover && \
 chmod +x ~/.local/bin/gover
 ```
 
+## System install (requires sudo)
+
+```
+sudo curl --tlsv1.2 -o /usr/local/bin/gover https://git.sr.ht/~whereswaldon/gover/blob/main/gover && \
+sudo chmod +x /usr/local/bin/gover
+```
+
+You will need to invoke `gover` as `sudo gover` each time you use it.
+
 ## Usage
 
 ```
-gover <minor> <patch>
+gover <version>
 ```
 
-This will activate go 1.`minor`.`patch` (installing it if needed).
+This will activate the specified version of `go` (installing it if needed).
+
+You can specify `latest` as a version to get the latest available version.
+
+If no version is specified, `latest` is assumed.
 
 ## Examples
 
 ```
+gover # assume latest and install
+gover latest # explicitly request latest
 gover 14 6 # install and activate go 1.14.6
 gover 13 14 # install and activate go 1.13.14
 gover 14 6 # activate go 1.14.6 (already installed)

@@ 1,5 1,6 @@
 #!/bin/sh
 # SPDX-License-Identifier: Unlicense OR MIT
+# Source: git.sr.ht/~whereswaldon/gover
 
 set -eu
 


@@ 8,26 9,34 @@ current_os() {
 }
 
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
-MINOR=${1:-14}
-PATCH=${2:-6}
+TARGET_VERSION=${1:-latest}
 PREFIX=${PREFIX:-$(dirname "$SCRIPT_DIR")}
+mkdir -p "$PREFIX"/lib
 GOOS=$(current_os)
 GOARCH=amd64 # TODO: find a portable way to determine this without go installed
 
+major() {
+    echo "$1" | cut -d. -f1
+}
+minor() {
+    echo "$1" | cut -d. -f2 || 0
+}
+patch() {
+    echo "$1" | cut -d. -f3 || 0
+}
+
 # version_dir emits the directory into which a particular go
 # version should be installed
 version_dir() {
-    if [ "$2" = "0" ]; then
-        echo "$PREFIX/lib/go-1.$1"
-        return 0
-    fi
-    echo "$PREFIX/lib/go-1.$1.$2"
+    target=$1
+    echo "$PREFIX/lib/go-$target"
 }
 
 # version_installed returns whether or not a particular version
 # of go is already installed
 version_installed() {
-    if [ -e "$(version_dir "$1" "$2")" ]; then
+    target=$1
+    if [ -e "$(version_dir "$target")" ]; then
         return 0
     fi
     return 1


@@ 35,23 44,19 @@ version_installed() {
 
 # install_version installs a particular version of go
 install_version() {
-    MINOR=$1
-    PATCH=$2
-    LIB_DIR=$(version_dir "$MINOR" "$PATCH")
-    FILENAME=go1.$MINOR.$PATCH.$GOOS-$GOARCH.tar.gz
-    if [ "$PATCH" = "0" ]; then
-    FILENAME=go1.$MINOR.$GOOS-$GOARCH.tar.gz
-    fi
+    target=$1
+    LIB_DIR=$(version_dir "$target")
+    FILENAME=go$target.$GOOS-$GOARCH.tar.gz
     DL_PATH=$LIB_DIR/../$FILENAME
     mkdir -p "$LIB_DIR"
     if ! curl -L -o "$DL_PATH" "https://golang.org/dl/$FILENAME"; then
-            echo "Couldn't download Go 1.$MINOR.$PATCH. Are you sure it exists?"
+            echo "Couldn't download Go $target. Are you sure it exists?"
             rm "$DL_PATH"
             rm -rf "$LIB_DIR"
             return 1
     fi
     if ! tar --strip-components=1 -xzC "$LIB_DIR" -f "$DL_PATH"; then
-            echo "Couldn't download Go 1.$MINOR.$PATCH. Are you sure it exists?"
+            echo "Couldn't uncompress Go $target."
             rm "$DL_PATH"
             rm -rf "$LIB_DIR"
             return 1


@@ 62,19 67,54 @@ install_version() {
 # activate_version symlinks a particular version of go to be the active
 # version
 activate_version() {
-    MINOR=$1
-    PATCH=$2
-    ln -svnf "$(version_dir "$1" "$2")/bin/go" "$PREFIX/bin/go"
+    target=$1
+    ln -svnf "$(version_dir "$target")/bin/go" "$PREFIX/bin/go"
+}
+
+# latest_version emits the latest version of go on stdout
+latest_version() {
+    versions=$(curl -q https://api.github.com/repos/golang/go/git/refs/tags | grep -e "\"ref\":" | grep -e "go" | grep -v -e "beta" -e "rc" | sed -E 's/.*go([[:digit:]]+(.[[:digit:]]+){0,2}).*/\1/')
+    highest_major=0
+    highest_minor=0
+    highest_patch=0
+    for version in $versions; do
+        major=$(major "$version")
+        if [ "$major" -gt "$highest_major" ]; then
+            highest_major=$major
+        fi
+    done
+    for version in $versions; do
+        major=$(major "$version")
+        minor=$(minor "$version")
+        if [ "$major" -eq "$highest_major" ] && [ "$minor" -gt "$highest_minor" ]; then
+            highest_minor=$minor
+        fi
+    done
+    for version in $versions; do
+        major=$(major "$version")
+        minor=$(minor "$version")
+        patch=$(patch "$version")
+        if [ "$major" -eq "$highest_major" ] && [ "$minor" -eq "$highest_minor" ] && [ "$patch" -gt "$highest_patch" ]; then
+            highest_patch=$patch
+        fi
+    done
+    if [ "$highest_minor" -eq 0 ] && [ "$highest_patch" -eq 0 ]; then echo "$highest_major"; return 0; fi
+    if [ "$highest_patch" -eq 0 ]; then echo "$highest_major.$highest_minor"; return 0; fi
+    echo "$highest_major.$highest_minor.$highest_patch"
 }
 
 gover() {
-    MINOR=$1
-    PATCH=$2
-    if ! version_installed "$MINOR" "$PATCH"; then
-        install_version "$MINOR" "$PATCH"
+    target="$1"
+    if [ "$target" = "latest" ]; then target=$(latest_version); fi
+    if [ "$target" = "-h" ] || [ "$target" = "--help" ]; then
+        printf "Usage: gover [version|latest]\n\nExamples:\n\tgover 1.15\n\tgover 1.7.1\n\tgover latest\n\tgover\n"
+        return 1
+    fi
+    if ! version_installed "$target"; then
+        install_version "$target"
     fi
-    activate_version "$MINOR" "$PATCH"
+    activate_version "$target"
     go version
 }
 
-gover "$MINOR" "$PATCH"
+gover "$TARGET_VERSION"