feat: Add gitHubLatestRelease template function

fix: lint failure

docs/REFERENCE.md

@@ -106,6 +106,7 @@ Manage your dotfiles across multiple machines, securely.
   * [`decrypt` *ciphertext*](#decrypt-ciphertext)
   * [`encrypt` *plaintext*](#encrypt-plaintext)
   * [`gitHubKeys` *user*](#githubkeys-user)
+  * [`gitHubLatestRelease` *user-repo*](#githubkeys-user-repo)
   * [`gopass` *gopass-name*](#gopass-gopass-name)
   * [`gopassRaw` *gopass-name*](#gopassraw-gopass-name)
   * [`include` *filename*](#include-filename)
@@ -2044,7 +2045,7 @@ environment variables `$CHEZMOI_GITHUB_ACCESS_TOKEN`, `$GITHUB_ACCESS_TOKEN`, or
 the GitHub API request, with a higher rate limit (currently 5,000 requests per
 hour per user).
 
-In practice, GitHub API rate limits are high enough that you should never need
+In practice, GitHub API rate limits are high enough that you should rarely need
 to set a token, unless you are sharing a source IP address with many other
 GitHub users. If needed, the GitHub documentation describes how to [create a
 personal access
@@ -2060,6 +2061,26 @@ token](https://docs.github.com/en/github/authenticating-to-github/creating-a-per
 
 ---
 
+### `gitHubLatestRelease` *user-repo*
+
+`gitHubLatestRelease` calls the GitHub API to retrieve the latest release about the given
+*user-repo*, returning structured data as defined by the [GitHub Go API
+bindings](https://pkg.go.dev/github.com/google/go-github/v40/github#RepositoryRelease).
+
+Calls to `gitHubLatestRelease` are cached so calling `gitHubLatestRelease` with the same
+*user-repo* will only result in one call to the GitHub API.
+
+
+`gitHubLatestRelease` uses the same API request mechanism as `gitHubKeys`.
+
+#### `gitHubLatestRelease` examples
+
+```
+{{ (gitHubLatestRelease "docker/compose").TagName }}
+```
+
+---
+
 ### `gopass` *gopass-name*
 
 `gopass` returns passwords stored in [gopass](https://www.gopass.pw/) using the

internal/cmd/config.go

@@ -404,6 +404,7 @@ func newConfig(options ...configOption) (*Config, error) {
 		"decrypt":                  c.decryptTemplateFunc,
 		"encrypt":                  c.encryptTemplateFunc,
 		"gitHubKeys":               c.gitHubKeysTemplateFunc,
+		"gitHubLatestRelease":      c.gitHubLatestReleaseTemplateFunc,
 		"gopass":                   c.gopassTemplateFunc,
 		"gopassRaw":                c.gopassRawTemplateFunc,
 		"include":                  c.includeTemplateFunc,

internal/cmd/githubtemplatefuncs.go

@@ -2,12 +2,15 @@ package cmd
 
 import (
 	"context"
+	"fmt"
+	"strings"
 
 	"github.com/google/go-github/v40/github"
 )
 
 type gitHubData struct {
-	keysCache map[string][]*github.Key
+	keysCache          map[string][]*github.Key
+	latestReleaseCache map[string]map[string]*github.RepositoryRelease
 }
 
 func (c *Config) gitHubKeysTemplateFunc(user string) []*github.Key {
@@ -43,3 +46,42 @@ func (c *Config) gitHubKeysTemplateFunc(user string) []*github.Key {
 	c.gitHub.keysCache[user] = allKeys
 	return allKeys
 }
+
+func (c *Config) gitHubLatestReleaseTemplateFunc(userRepo string) *github.RepositoryRelease {
+	user, repo := parseGitHubUserRepo(userRepo)
+
+	if release := c.gitHub.latestReleaseCache[user][repo]; release != nil {
+		return release
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	gitHubClient := newGitHubClient(ctx)
+
+	release, _, err := gitHubClient.Repositories.GetLatestRelease(ctx, user, repo)
+	if err != nil {
+		returnTemplateError(err)
+		return nil
+	}
+
+	if c.gitHub.latestReleaseCache == nil {
+		c.gitHub.latestReleaseCache = make(map[string]map[string]*github.RepositoryRelease)
+	}
+	if c.gitHub.latestReleaseCache[user] == nil {
+		c.gitHub.latestReleaseCache[user] = make(map[string]*github.RepositoryRelease)
+	}
+	c.gitHub.latestReleaseCache[user][repo] = release
+
+	return release
+}
+
+func parseGitHubUserRepo(userRepo string) (string, string) {
+	fields := strings.SplitN(userRepo, "/", 2)
+	if len(fields) != 2 || fields[0] == "" || fields[1] == "" {
+		returnTemplateError(fmt.Errorf("%s: not a user/repo", userRepo))
+		return "", ""
+	}
+	user, repo := fields[0], fields[1]
+	return user, repo
+}