Update nns and sns extensions pinned version (#350)

# Motivation

We haven't updated the version of the `nns` and `sns` extensions we use
in some time.
It's not possible to upgrade an extension, so we used to be stuck with
one version but now it's at least possible to uninstall and reinstall.

# Changes

1. Add `bin/dfx-software-dfx-extension-install` to hold the shared code
between `bin/dfx-software-dfx-extension-nns-install` and
`bin/dfx-software-dfx-extension-sns-install`.
2. Check the current installed version and uninstall if it's different
from the desired version.

Note that when the "latest" version is requested, we don't ask for a
specific version but take what we get. We don't know ahead of time what
we'll get so in this case we always uninstall first.

# Tested

Tested manually by installing with `--version 0.2.1`, with `--version
latest` and `--version pinned`.

bin/dfx-software-dfx-extension-install

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SOURCE_DIR="$(dirname "${BASH_SOURCE[0]}")"
+PATH="$SOURCE_DIR:$PATH"
+
+print_help() {
+  cat <<-EOF
+	Installs a dfx extension.
+	EOF
+}
+
+# Source the clap.bash file ---------------------------------------------------
+source "$SOURCE_DIR/clap.bash"
+# Define options
+clap.define short=e long=extension desc="The extension to install." variable=EXTENSION default=""
+clap.define short=v long=version desc="The version of the extension to install" variable=VERSION default="latest"
+# Source the output file ----------------------------------------------------------
+source "$(clap.build)"
+
+if [[ -z "$EXTENSION" ]]; then
+  echo "Error: --extension must be set. For example to 'nns' or 'sns'." >&2
+  exit 1
+fi
+
+if [[ "$VERSION" = "latest" ]]; then
+  VERSION_ARGS=()
+else
+  VERSION_ARGS=("--version" "$VERSION")
+fi
+
+is_installed() {
+  dfx extension list | grep -w "$EXTENSION"
+}
+
+get_current_version() {
+  jq -r .version "$(dfx cache show)/extensions/$EXTENSION/extension.json"
+}
+
+if is_installed; then
+  current_version="$(get_current_version)"
+  if [[ "$current_version" = "$VERSION" ]]; then
+    echo "$EXTENSION extension version $VERSION is already installed."
+    exit 0
+  fi
+  echo "Uninstalling current $EXTENSION extension version $current_version."
+  dfx extension uninstall "$EXTENSION"
+fi
+
+dfx extension install "$EXTENSION" "${VERSION_ARGS[@]}"
+echo "Installed $EXTENSION dfx extension version $(get_current_version)"

bin/dfx-software-dfx-extension-nns-install

@@ -22,20 +22,4 @@ if [[ "$VERSION" = "pinned" ]]; then
   VERSION="$DFX_NNS_EXTENSION_VERSION"
 fi
 
-if [[ "$VERSION" = "latest" ]]; then
-  VERSION_ARGS=()
-else
-  VERSION_ARGS=("--version" "$VERSION")
-fi
-
-is_installed() {
-  dfx extension list | grep -w nns
-}
-
-if is_installed; then
-  : "Unfortunately there is currently no way to check which version is installed or to upgrade to a different version."
-  echo "nns extension is already installed" >&2
-  exit 0
-fi
-
-dfx extension install nns "${VERSION_ARGS[@]}"
+dfx-software-dfx-extension-install --extension nns --version "$VERSION"

bin/dfx-software-dfx-extension-sns-install

@@ -22,20 +22,4 @@ if [[ "$VERSION" = "pinned" ]]; then
   VERSION="$DFX_SNS_EXTENSION_VERSION"
 fi
 
-if [[ "$VERSION" = "latest" ]]; then
-  VERSION_ARGS=()
-else
-  VERSION_ARGS=("--version" "$VERSION")
-fi
-
-is_installed() {
-  dfx extension list | grep -w sns
-}
-
-if is_installed; then
-  : "Unfortunately there is currently no way to check which version is installed or to upgrade to a different version."
-  echo "sns extension is already installed" >&2
-  exit 0
-fi
-
-dfx extension install sns "${VERSION_ARGS[@]}"
+dfx-software-dfx-extension-install --extension sns --version "$VERSION"

bin/versions.bash

@@ -10,5 +10,5 @@ QUILL_VERSION=0.4.0
 IDL2JSON_VERSION=0.8.5
 BINSTALL_VERSION=1.3.0
 IC_WASM_VERSION=0.6.0
-DFX_NNS_EXTENSION_VERSION=0.2.1
-DFX_SNS_EXTENSION_VERSION=0.2.1
+DFX_NNS_EXTENSION_VERSION=0.4.0
+DFX_SNS_EXTENSION_VERSION=0.4.0