adding airgap install instructions (#964)

* adding airgap install instructions

* remove extraneous lines

* remove extraneous comments that did not apply to final code, applied shell script formatting

* update readme to add concrete examples and follow syntax and formatting of the rest of the document

* running shfmt -w on bash script/

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* updating readme to specify grabbing correct architecture

* moving git version check to online install only

---------

Co-authored-by: Matt Fletcher <mfletcher36@gatech.edu>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

README.md

@@ -21,6 +21,26 @@ This can also be used to compare two revisions/versions of your helm release.
 helm plugin install https://github.com/databus23/helm-diff
 ```
 
+### Installing offline
+
+If installing this in an offline/airgapped environment, download the platform-specific binary archive (e.g., `helm-diff-linux-amd64.tgz` or `helm-diff-windows-amd64.tgz`) from [releases](https://github.com/databus23/helm-diff/releases). Make sure to select the correct `.tgz` file for your operating system and architecture.
+
+Set `HELM_DIFF_BIN_TGZ` to the absolute path to the downloaded binary archive:
+
+**POSIX shell:**
+```sh
+export HELM_DIFF_BIN_TGZ=/path/to/helm-diff-linux-amd64.tgz
+
+
+**PowerShell:**
+```powershell
+$env:HELM_DIFF_BIN_TGZ = "C:\path\to\helm-diff-bin.tgz"
+```
+
+Now, run `helm plugin install /path/to/helm-diff/`.
+Here, `/path/to/helm-diff/` must be a local copy of the Helm Diff plugin source directory (including `plugin.yaml` and the install scripts), for example from a repo you cloned or a source archive you downloaded earlier and transferred into the offline environment.
+The install script will skip the GitHub download and instead install from the `.tgz`.
+
 **For Helm 4 users:**
 
 Helm 4 requires plugin verification by default. Since this plugin does not yet provide provenance artifacts, you need to use the `--verify=false` flag:

install-binary.ps1

@@ -4,27 +4,22 @@ param (
 
 function Get-Architecture {
   $architecture = [System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture
-
   $arch = switch ($architecture) {
-    "X64"  { "amd64" }
+    "X64"   { "amd64" }
     "Arm64" { "arm64" }
     Default { "" }
   }
-
   if ($arch -eq "") {
     throw "Unsupported architecture: ${architecture}"
   }
-
   return $arch
 }
 
 function Get-Version {
   param ([Parameter(Mandatory=$true)][bool] $Update)
-
   if ($Update) {
     return "latest"
   }
-
   return git describe --tags --exact-match 2>$null || "latest"
 }
 
@@ -37,7 +32,6 @@ function New-TemporaryDirectory {
 
 function Get-Url {
   param ([Parameter(Mandatory=$true)][string] $Version, [Parameter(Mandatory=$true)][string] $Architecture)
-
   if ($Version -eq "latest") {
     return "https://github.com/databus23/helm-diff/releases/latest/download/helm-diff-windows-${Architecture}.tgz"
   }
@@ -46,17 +40,14 @@ function Get-Url {
 
 function Download-Plugin {
   param ([Parameter(Mandatory=$true)][string] $Url, [Parameter(Mandatory=$true)][string] $Output)
-
   Invoke-WebRequest -OutFile $Output $Url
 }
 
 function Install-Plugin {
   param ([Parameter(Mandatory=$true)][string] $ArchiveDirectory, [Parameter(Mandatory=$true)][string] $ArchiveName, [Parameter(Mandatory=$true)][string] $Destination)
-
   Push-Location $ArchiveDirectory
-  tar -xzf $ArchiveName -C . 
+  tar -xzf $ArchiveName -C .
   Pop-Location
-
   New-Item -ItemType Directory -Path $Destination -Force
   Copy-Item -Path (Join-Path $ArchiveDirectory "diff" "bin" "diff.exe") -Destination $Destination -Force
 }
@@ -65,13 +56,23 @@ $ErrorActionPreference = "Stop"
 
 $archiveName = "helm-diff.tgz"
 $arch = Get-Architecture
-$version = Get-Version -Update $Update
 $tmpDir = New-TemporaryDirectory
-
-trap {  Remove-Item -path $tmpDir -Recurse -Force }
-
-$url = Get-Url -Version $version -Architecture $arch
+trap {   Remove-Item -path $tmpDir -Recurse -Force }
 $output = Join-Path $tmpDir $archiveName
 
-Download-Plugin -Url $url -Output $output
-Install-Plugin -ArchiveDirectory $tmpDir -ArchiveName $archiveName -Destination (Join-Path $env:HELM_PLUGIN_DIR "bin")
+# Check for offline installation via environment variable
+if ($env:HELM_DIFF_BIN_TGZ) {
+    Write-Host "HELM_DIFF_BIN_TGZ is set. Using local package at: $($env:HELM_DIFF_BIN_TGZ)"
+    if (-not (Test-Path $env:HELM_DIFF_BIN_TGZ -PathType Leaf)) {
+        throw "Offline installation failed: File not found at '$($env:HELM_DIFF_BIN_TGZ)'"
+    }
+    Copy-Item -Path $env:HELM_DIFF_BIN_TGZ -Destination $output
+}
+else {
+    # Proceed with online installation
+    $version = Get-Version -Update $Update
+    $url = Get-Url -Version $version -Architecture $arch
+    Download-Plugin -Url $url -Output $output
+}
+
+Install-Plugin -ArchiveDirectory $tmpDir -ArchiveName $archiveName -Destination (Join-Path $env:HELM_PLUGIN_DIR "bin")

install-binary.sh

@@ -10,18 +10,14 @@ export GREP_COLOR="never"
 # available. This is the case when using MSYS2 or Cygwin
 # on Windows where helm returns a Windows path but we
 # need a Unix path
-
 if command -v cygpath >/dev/null 2>&1; then
   HELM_BIN="$(cygpath -u "${HELM_BIN}")"
   HELM_PLUGIN_DIR="$(cygpath -u "${HELM_PLUGIN_DIR}")"
 fi
 
 [ -z "$HELM_BIN" ] && HELM_BIN=$(command -v helm)
-
 [ -z "$HELM_HOME" ] && HELM_HOME=$(helm env | grep 'HELM_DATA_HOME' | cut -d '=' -f2 | tr -d '"')
-
 mkdir -p "$HELM_HOME"
-
 : "${HELM_PLUGIN_DIR:="$HELM_HOME/plugins/helm-diff"}"
 
 if [ "$SKIP_BIN_INSTALL" = "1" ]; then
@@ -55,7 +51,6 @@ initArch() {
 # initOS discovers the operating system for this system.
 initOS() {
   OS=$(uname -s)
-
   case "$OS" in
   Windows_NT) OS='windows' ;;
   # Msys support
@@ -77,16 +72,21 @@ verifySupported() {
     exit 1
   fi
 
-  if
-    ! command -v curl >/dev/null 2>&1 && ! command -v wget >/dev/null 2>&1
-  then
-    echo "Either curl or wget is required"
-    exit 1
+  # Skip download tool check if using local file
+  if [ -z "$HELM_DIFF_BIN_TGZ" ]; then
+    if ! command -v curl >/dev/null 2>&1 && ! command -v wget >/dev/null 2>&1; then
+      echo "Either curl or wget is required"
+      exit 1
+    fi
   fi
 }
 
 # getDownloadURL checks the latest available version.
 getDownloadURL() {
+  # If HELM_DIFF_BIN_TGZ is set, we don't need a download URL
+  if [ -n "$HELM_DIFF_BIN_TGZ" ]; then
+    return
+  fi
   version=$(git -C "$HELM_PLUGIN_DIR" describe --tags --exact-match 2>/dev/null || :)
   if [ "$SCRIPT_MODE" = "install" ] && [ -n "$version" ]; then
     DOWNLOAD_URL="https://github.com/$PROJECT_GH/releases/download/$version/helm-diff-$OS-$ARCH.tgz"
@@ -99,6 +99,7 @@ getDownloadURL() {
 mkTempDir() {
   HELM_TMP="$(mktemp -d -t "${PROJECT_NAME}-XXXXXX")"
 }
+
 rmTempDir() {
   if [ -d "${HELM_TMP:-/tmp/helm-diff-tmp}" ]; then
     rm -rf "${HELM_TMP:-/tmp/helm-diff-tmp}"
@@ -109,21 +110,29 @@ rmTempDir() {
 # for that binary.
 downloadFile() {
   PLUGIN_TMP_FILE="${HELM_TMP}/${PROJECT_NAME}.tgz"
+
+  # If HELM_DIFF_BIN_TGZ is set, copy the local file instead of downloading
+  if [ -n "$HELM_DIFF_BIN_TGZ" ]; then
+    echo "Using local package at $HELM_DIFF_BIN_TGZ"
+    if [ ! -f "$HELM_DIFF_BIN_TGZ" ]; then
+      echo "Error: file not found at $HELM_DIFF_BIN_TGZ"
+      exit 1
+    fi
+    cp "$HELM_DIFF_BIN_TGZ" "$PLUGIN_TMP_FILE"
+    return
+  fi
+
   echo "Downloading $DOWNLOAD_URL"
-  if
-    command -v curl >/dev/null 2>&1
-  then
+  if command -v curl >/dev/null 2>&1; then
     curl -sSf -L "$DOWNLOAD_URL" >"$PLUGIN_TMP_FILE"
-  elif
-    command -v wget >/dev/null 2>&1
-  then
+  elif command -v wget >/dev/null 2>&1; then
     wget -q -O - "$DOWNLOAD_URL" >"$PLUGIN_TMP_FILE"
   fi
 }
 
-# installFile verifies the SHA256 for the file, then unpacks and
-# installs it.
+# Unpack the archive file, then install it into the helm directory.
 installFile() {
+  PLUGIN_TMP_FILE="${HELM_TMP}/${PROJECT_NAME}.tgz"
   tar xzf "$PLUGIN_TMP_FILE" -C "$HELM_TMP"
   HELM_TMP_BIN="$HELM_TMP/diff/bin/diff"
   if [ "${OS}" = "windows" ]; then
@@ -145,11 +154,11 @@ exit_trap() {
   exit $result
 }
 
-# Execution
-
-#Stop execution on any error
+# --- Execution ---
+# Stop execution on any error
 trap "exit_trap" EXIT
 set -e
+
 initArch
 initOS
 verifySupported