doctl: Resolve versions based on GitHub releases

Previously, doctl was pinned to a rather old release (1.56.0). Use the
`GitHubVersionStrategy` to find versions based on GH releases, and simplify URL
construction by providing a `BinaryTemplate` rather than a full `URLTemplate`,
since the binaries live at standard GitHub release paths.

While we're here, add support for doctl Linux ARM binaries since they are now
available.

Signed-off-by: Adam Wolfe Gordon <awg@xvx.ca>

pkg/get/get_test.go

@@ -1075,7 +1075,7 @@ func Test_DownloadDigitalOcean(t *testing.T) {
 
 	tool := getTool(name, tools)
 
-	const toolVersion = "1.46.0"
+	const toolVersion = "v1.46.0"
 	const urlTemplate = "https://github.com/digitalocean/doctl/releases/download/v1.46.0/doctl-1.46.0-%s-%s.%s"
 
 	tests := []test{
@@ -1091,11 +1091,10 @@ func Test_DownloadDigitalOcean(t *testing.T) {
 			arch:    arch64bit,
 			version: toolVersion,
 			url:     fmt.Sprintf(urlTemplate, "darwin", "amd64", "tar.gz")},
-		// this asserts that we can build a URL for ARM processors, but no asset exists and will yield a 404
 		{os: "linux",
 			arch:    archARM7,
 			version: toolVersion,
-			url:     fmt.Sprintf(urlTemplate, "linux", "", "tar.gz")},
+			url:     fmt.Sprintf(urlTemplate, "linux", "arm64", "tar.gz")},
 	}
 
 	for _, tc := range tests {

pkg/get/tools.go

@@ -642,34 +642,32 @@ https://github.com/inlets/inletsctl/releases/download/{{.Version}}/{{$fileName}}
 
 	tools = append(tools,
 		Tool{
-			Owner:       "digitalocean",
-			Repo:        "doctl",
-			Name:        "doctl",
-			Version:     "1.56.0",
-			Description: "Official command line interface for the DigitalOcean API.",
-			URLTemplate: `
-		{{$osStr := ""}}
+			Owner:           "digitalocean",
+			Repo:            "doctl",
+			Name:            "doctl",
+			VersionStrategy: GitHubVersionStrategy,
+			Description:     "Official command line interface for the DigitalOcean API.",
+			BinaryTemplate: `
+		{{$osStr := .OS}}
 		{{ if HasPrefix .OS "ming" -}}
 		{{$osStr = "windows"}}
-		{{- else if eq .OS "linux" -}}
-		{{$osStr = "linux"}}
-		{{- else if eq .OS "darwin" -}}
-		{{$osStr = "darwin"}}
 		{{- end -}}
 
-		{{$archStr := ""}}
+		{{$archStr := .Arch}}
 		{{- if eq .Arch "x86_64" -}}
 		{{$archStr = "amd64"}}
+		{{- else if eq .Arch "armv7l" }}
+		{{$archStr = "arm64"}}
+		{{- else if eq .Arch "aarch64" }}
+		{{$archStr = "arm64"}}
 		{{- end -}}
 
-		{{$archiveStr := ""}}
-		{{ if HasPrefix .OS "ming" -}}
+		{{$archiveStr := "tar.gz"}}
+		{{ if eq $osStr "windows" -}}
 		{{$archiveStr = "zip"}}
-		{{- else -}}
-		{{$archiveStr = "tar.gz"}}
 		{{- end -}}
 
-		https://github.com/digitalocean/doctl/releases/download/v{{.Version}}/doctl-{{.Version}}-{{$osStr}}-{{$archStr}}.{{$archiveStr}}`,
+		doctl-{{.VersionNumber}}-{{$osStr}}-{{$archStr}}.{{$archiveStr}}`,
 		})
 
 	tools = append(tools,