Add nodocs and noembeddocs build tags (#431)

Add nodocs and noembeddocs build tags

cmd/docs.go

@@ -1,11 +1,12 @@
+// +build !nodocs
+
 package cmd
 
 import (
 	"fmt"
 	"regexp"
 	"strings"
 
-	packr "github.com/gobuffalo/packr/v2"
 	"github.com/spf13/cobra"
 	vfs "github.com/twpayne/go-vfs"
 )
@@ -24,16 +25,19 @@ func init() {
 }
 
 func (c *Config) runDocsCmd(fs vfs.FS, args []string) error {
-	box := packr.New("docs", "../docs")
 	filename := "REFERENCE.md"
 	if len(args) > 0 {
 		pattern := args[0]
 		re, err := regexp.Compile(strings.ToLower(pattern))
 		if err != nil {
 			return err
 		}
+		docsFilenames, err := getDocsFilenames()
+		if err != nil {
+			return err
+		}
 		var filenames []string
-		for _, fn := range box.List() {
+		for _, fn := range docsFilenames {
 			if re.FindStringIndex(strings.ToLower(fn)) != nil {
 				filenames = append(filenames, fn)
 			}
@@ -47,7 +51,7 @@ func (c *Config) runDocsCmd(fs vfs.FS, args []string) error {
 			return fmt.Errorf("%s: ambiguous pattern, matches %s", pattern, strings.Join(filenames, ", "))
 		}
 	}
-	data, err := box.Find(filename)
+	data, err := getDoc(filename)
 	if err != nil {
 		return err
 	}

cmd/docs_embeddocs.go

@@ -0,0 +1,19 @@
+// +build !nodocs
+// +build !noembeddocs
+
+package cmd
+
+import packr "github.com/gobuffalo/packr/v2"
+
+// DocsDir is unused when chezmoi is built with embedded docs.
+var DocsDir = ""
+
+var docsBox = packr.New("docs", "../docs")
+
+func getDocsFilenames() ([]string, error) {
+	return docsBox.List(), nil
+}
+
+func getDoc(filename string) ([]byte, error) {
+	return docsBox.Find(filename)
+}

cmd/docs_noembeddocs.go

@@ -0,0 +1,27 @@
+// +build !nodocs
+// +build noembeddocs
+
+package cmd
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// DocsDir is the directory containing docs when chezmoi is built without
+// embedded docs. It should be an absolute path.
+var DocsDir = "docs"
+
+func getDocsFilenames() ([]string, error) {
+	f, err := os.Open(DocsDir)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	return f.Readdirnames(-1)
+}
+
+func getDoc(filename string) ([]byte, error) {
+	return ioutil.ReadFile(filepath.Join(DocsDir, filename))
+}

docs/CONTRIBUTING.md

@@ -96,6 +96,19 @@ If you plan to package chezmoi for your distibution, then note:
 * Please enable CGO, if possible. chezmoi can be built and run without CGO, but
   the `.chezmoi.group` template variable may not be set on some systems.
 
+* chezmoi includes a `docs` command which prints its documentation. By default,
+  the docs are embedded in the binary. You can disable this behaviour, and have
+  chezmoi read its docs from the filesystem by building with the `noembeddocs`
+  build tag and setting the directory where chezmoi can find them with the `-X
+  github.com/twpayne/chezmoi/cmd.DocDir={{ .PathToDocs }}` linker flag. For
+  example:
+
+  ```
+  go build -tags noembeddocs -ldflags "-X github.com/twpayne/chezmoi/cmd.DocsDir=/usr/share/doc/chezmoi" .
+  ```
+
+  To disable the `docs` command completely, use the `nodocs` build tag.
+
 * chezmoi includes an `upgrade` command which attempts to self-upgrade. You can
   remove this command completely by building chezmoi with the `noupgrade` build
   tag.