feat(cmd): add support for build tags (#52)

README.md

@@ -49,6 +49,7 @@ Flags:
       --repository.default-branch string   Manual override for the git repository URL used in place of automatic detection.
       --repository.path string             Manual override for the path from the root of the git repository used in place of automatic detection.
       --repository.url string              Manual override for the git repository URL used in place of automatic detection.
+      --tags strings                       Set of build tags to apply when choosing which files to include for documentation generation.
   -t, --template stringToString            Custom template string to use for the provided template name instead of the default template. (default [])
       --template-file stringToString       Custom template file to use for the provided template name instead of the default template. (default [])
   -v, --verbose count                      Log additional output from the execution of the command. Can be chained for additional verbosity.
@@ -131,6 +132,12 @@ As with the godoc tool itself\, only exported symbols will be shown in documenta
 gomarkdoc -u -o README.md .
 ```
 
+If you would like to include files that are part of a build tag\, you can specify build tags with the \-\-tags flag\. Tags are also supported through GOFLAGS\, though command line and configuration file definitions override tags specified through GOFLAGS\.
+
+```
+gomarkdoc --tags sometag .
+```
+
 You can also run gomarkdoc in a verification mode with the \-\-check/\-c flag\. This is particularly useful for continuous integration when you want to make sure that a commit correctly updated the generated documentation\. This flag is only supported when the \-\-output/\-o flag is specified\, as the file provided there is what the tool is checking:
 
 ```

cmd/gomarkdoc/README.md

@@ -15,7 +15,7 @@ See https://github.com/princjef/gomarkdoc for full documentation of this tool\.
 - [type PackageSpec](<#type-packagespec>)
 
 
-## type [PackageSpec](<https://github.com/princjef/gomarkdoc/blob/master/cmd/gomarkdoc/command.go#L30-L44>)
+## type [PackageSpec](<https://github.com/princjef/gomarkdoc/blob/master/cmd/gomarkdoc/command.go#L31-L45>)
 
 PackageSpec defines the data available to the \-\-output option's template\. Information is recomputed for each package generated\.
 

cmd/gomarkdoc/command.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"container/list"
 	"errors"
+	"flag"
 	"fmt"
 	"go/build"
 	"hash/fnv"
@@ -51,6 +52,7 @@ type commandOptions struct {
 	footer                string
 	footerFile            string
 	format                string
+	tags                  []string
 	templateOverrides     map[string]string
 	templateFileOverrides map[string]string
 	verbosity             int
@@ -90,6 +92,7 @@ func buildCommand() *cobra.Command {
 			opts.headerFile = viper.GetString("headerFile")
 			opts.footer = viper.GetString("footer")
 			opts.footerFile = viper.GetString("footerFile")
+			opts.tags = viper.GetStringSlice("tags")
 			opts.repository.Remote = viper.GetString("repository.url")
 			opts.repository.DefaultBranch = viper.GetString("repository.defaultBranch")
 			opts.repository.PathFromRoot = viper.GetString("repository.path")
@@ -180,6 +183,12 @@ func buildCommand() *cobra.Command {
 		"",
 		"File containing additional content to inject at the end of each output file.",
 	)
+	command.Flags().StringSliceVar(
+		&opts.tags,
+		"tags",
+		defaultTags(),
+		"Set of build tags to apply when choosing which files to include for documentation generation.",
+	)
 	command.Flags().CountVarP(
 		&opts.verbosity,
 		"verbose",
@@ -222,13 +231,34 @@ func buildCommand() *cobra.Command {
 	_ = viper.BindPFlag("headerFile", command.Flags().Lookup("header-file"))
 	_ = viper.BindPFlag("footer", command.Flags().Lookup("footer"))
 	_ = viper.BindPFlag("footerFile", command.Flags().Lookup("footer-file"))
+	_ = viper.BindPFlag("tags", command.Flags().Lookup("tags"))
 	_ = viper.BindPFlag("repository.url", command.Flags().Lookup("repository.url"))
 	_ = viper.BindPFlag("repository.defaultBranch", command.Flags().Lookup("repository.default-branch"))
 	_ = viper.BindPFlag("repository.path", command.Flags().Lookup("repository.path"))
 
 	return command
 }
 
+func defaultTags() []string {
+	f, ok := os.LookupEnv("GOFLAGS")
+	if !ok {
+		return nil
+	}
+
+	fs := flag.NewFlagSet("goflags", flag.ContinueOnError)
+	tags := fs.String("tags", "", "")
+
+	if err := fs.Parse(strings.Fields(f)); err != nil {
+		return nil
+	}
+
+	if tags == nil {
+		return nil
+	}
+
+	return strings.Split(*tags, ",")
+}
+
 func buildConfig(configFile string) {
 	if configFile != "" {
 		viper.SetConfigFile(configFile)
@@ -364,7 +394,7 @@ func loadPackages(specs []*PackageSpec, opts commandOptions) error {
 	for _, spec := range specs {
 		log := logger.New(getLogLevel(opts.verbosity), logger.WithField("dir", spec.Dir))
 
-		buildPkg, err := getBuildPackage(spec.ImportPath)
+		buildPkg, err := getBuildPackage(spec.ImportPath, opts.tags)
 		if err != nil {
 			log.Debugf("unable to load package in directory: %s", err)
 			// We don't care if a wildcard path produces nothing
@@ -493,9 +523,12 @@ func checkFile(b *bytes.Buffer, path string) error {
 	return nil
 }
 
-func getBuildPackage(path string) (*build.Package, error) {
+func getBuildPackage(path string, tags []string) (*build.Package, error) {
+	ctx := build.Default
+	ctx.BuildTags = tags
+
 	if isLocalPath(path) {
-		pkg, err := build.ImportDir(path, build.ImportComment)
+		pkg, err := ctx.ImportDir(path, build.ImportComment)
 		if err != nil {
 			return nil, fmt.Errorf("gomarkdoc: invalid package in directory: %s", path)
 		}
@@ -508,7 +541,7 @@ func getBuildPackage(path string) (*build.Package, error) {
 		return nil, err
 	}
 
-	pkg, err := build.Import(path, wd, build.ImportComment)
+	pkg, err := ctx.Import(path, wd, build.ImportComment)
 	if err != nil {
 		return nil, fmt.Errorf("gomarkdoc: invalid package at import path: %s", path)
 	}

doc.go

@@ -38,6 +38,7 @@
 // 	      --repository.default-branch string   Manual override for the git repository URL used in place of automatic detection.
 // 	      --repository.path string             Manual override for the path from the root of the git repository used in place of automatic detection.
 // 	      --repository.url string              Manual override for the git repository URL used in place of automatic detection.
+//	      --tags strings                       Set of build tags to apply when choosing which files to include for documentation generation.
 // 	  -t, --template stringToString            Custom template string to use for the provided template name instead of the default template. (default [])
 // 	      --template-file stringToString       Custom template file to use for the provided template name instead of the default template. (default [])
 // 	  -v, --verbose count                      Log additional output from the execution of the command. Can be chained for additional verbosity.
@@ -137,6 +138,13 @@
 //
 //	gomarkdoc -u -o README.md .
 //
+// If you would like to include files that are part of a build tag, you can
+// specify build tags with the --tags flag. Tags are also supported through
+// GOFLAGS, though command line and configuration file definitions override tags
+// specified through GOFLAGS.
+//
+//	gomarkdoc --tags sometag .
+//
 // You can also run gomarkdoc in a verification mode with the --check/-c flag.
 // This is particularly useful for continuous integration when you want to make
 // sure that a commit correctly updated the generated documentation. This flag