Add command-specific argument completions

Complete bug IDs, bridges, users, labels where appropriate.

This works in bash and fish. ZSH is not yet supported by Cobra.
In fish, descriptions (the part of a completion after the "\t") are shown
as completion label, and can be searched with Ctrl+S.

Reproduce with

	fish -C 'source misc/fish_completion/git-bug'
	git bug select ^I

(tested with fish version 3.3.1)

Also works with bash, but only for "git-bug" (with the dash)

	bash --rcfile <(echo source misc/bash_completion/git-bug)
	git-bug select ^I

Closes #493

26 files changed, 475 insertions, 7 deletions

diff --git a/commands/bridge_auth_addtoken.go b/commands/bridge_auth_addtoken.go
index c0458fda..dfdc66b6 100644
--- a/commands/bridge_auth_addtoken.go
+++ b/commands/bridge_auth_addtoken.go
@@ -41,10 +41,12 @@ func newBridgeAuthAddTokenCommand() *cobra.Command {
 
 	flags.StringVarP(&options.target, "target", "t", "",
 		fmt.Sprintf("The target of the bridge. Valid values are [%s]", strings.Join(bridge.Targets(), ",")))
+	cmd.RegisterFlagCompletionFunc("target", completeFrom(bridge.Targets()))
 	flags.StringVarP(&options.login,
 		"login", "l", "", "The login in the remote bug-tracker")
 	flags.StringVarP(&options.user,
 		"user", "u", "", "The user to add the token to. Default is the current user")
+	cmd.RegisterFlagCompletionFunc("user", completeUser(env))
 
 	return cmd
 }
diff --git a/commands/bridge_auth_rm.go b/commands/bridge_auth_rm.go
index fa73ad11..a28057de 100644
--- a/commands/bridge_auth_rm.go
+++ b/commands/bridge_auth_rm.go
@@ -16,7 +16,8 @@ func newBridgeAuthRm() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runBridgeAuthRm(env, args)
 		},
-		Args: cobra.ExactArgs(1),
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: completeBridgeAuth(env),
 	}
 
 	return cmd
diff --git a/commands/bridge_auth_show.go b/commands/bridge_auth_show.go
index f174cdb7..7233bb51 100644
--- a/commands/bridge_auth_show.go
+++ b/commands/bridge_auth_show.go
@@ -21,7 +21,8 @@ func newBridgeAuthShow() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runBridgeAuthShow(env, args)
 		}),
-		Args: cobra.ExactArgs(1),
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: completeBridgeAuth(env),
 	}
 
 	return cmd
diff --git a/commands/bridge_configure.go b/commands/bridge_configure.go
index 6533e497..bbfc13be 100644
--- a/commands/bridge_configure.go
+++ b/commands/bridge_configure.go
@@ -97,6 +97,7 @@ git bug bridge configure \
 	flags.StringVarP(&options.name, "name", "n", "", "A distinctive name to identify the bridge")
 	flags.StringVarP(&options.target, "target", "t", "",
 		fmt.Sprintf("The target of the bridge. Valid values are [%s]", strings.Join(bridge.Targets(), ",")))
+	cmd.RegisterFlagCompletionFunc("target", completeFrom(bridge.Targets()))
 	flags.StringVarP(&options.params.URL, "url", "u", "", "The URL of the remote repository")
 	flags.StringVarP(&options.params.BaseURL, "base-url", "b", "", "The base URL of your remote issue tracker")
 	flags.StringVarP(&options.params.Login, "login", "l", "", "The login on your remote issue tracker")
diff --git a/commands/bridge_pull.go b/commands/bridge_pull.go
index 3155ebf4..9370e088 100644
--- a/commands/bridge_pull.go
+++ b/commands/bridge_pull.go
@@ -32,7 +32,8 @@ func newBridgePullCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runBridgePull(env, options, args)
 		}),
-		Args: cobra.MaximumNArgs(1),
+		Args:              cobra.MaximumNArgs(1),
+		ValidArgsFunction: completeBridge(env),
 	}
 
 	flags := cmd.Flags()
diff --git a/commands/bridge_push.go b/commands/bridge_push.go
index a232f0f0..ef1f2d3e 100644
--- a/commands/bridge_push.go
+++ b/commands/bridge_push.go
@@ -23,7 +23,8 @@ func newBridgePushCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runBridgePush(env, args)
 		}),
-		Args: cobra.MaximumNArgs(1),
+		Args:              cobra.MaximumNArgs(1),
+		ValidArgsFunction: completeBridge(env),
 	}
 
 	return cmd
diff --git a/commands/bridge_rm.go b/commands/bridge_rm.go
index 121a35ad..0306944e 100644
--- a/commands/bridge_rm.go
+++ b/commands/bridge_rm.go
@@ -16,7 +16,8 @@ func newBridgeRm() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runBridgeRm(env, args)
 		}),
-		Args: cobra.ExactArgs(1),
+		Args:              cobra.ExactArgs(1),
+		ValidArgsFunction: completeBridge(env),
 	}
 
 	return cmd
diff --git a/commands/comment.go b/commands/comment.go
index 90657e4a..b4b4628b 100644
--- a/commands/comment.go
+++ b/commands/comment.go
@@ -18,6 +18,7 @@ func newCommentCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runComment(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	cmd.AddCommand(newCommentAddCommand())
diff --git a/commands/comment_add.go b/commands/comment_add.go
index 11ba5ad3..f308428c 100644
--- a/commands/comment_add.go
+++ b/commands/comment_add.go
@@ -25,6 +25,7 @@ func newCommentAddCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runCommentAdd(env, options, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	flags := cmd.Flags()
diff --git a/commands/helper_completion.go b/commands/helper_completion.go
new file mode 100644
index 00000000..a23e810f
--- /dev/null
+++ b/commands/helper_completion.go
@@ -0,0 +1,350 @@
+package commands
+
+import (
+	"sort"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	"github.com/MichaelMure/git-bug/bridge"
+	"github.com/MichaelMure/git-bug/bridge/core/auth"
+	"github.com/MichaelMure/git-bug/bug"
+	"github.com/MichaelMure/git-bug/cache"
+	_select "github.com/MichaelMure/git-bug/commands/select"
+)
+
+type validArgsFunction func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective)
+
+func completionHandlerError(err error) (completions []string, directives cobra.ShellCompDirective) {
+	return nil, cobra.ShellCompDirectiveError
+}
+
+func completeBridge(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		bridges, err := bridge.ConfiguredBridges(env.backend)
+		if err != nil {
+			return completionHandlerError(err)
+		}
+
+		completions = make([]string, len(bridges))
+		for i, bridge := range bridges {
+			completions[i] = bridge + "\t" + "Bridge"
+		}
+
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeBridgeAuth(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		creds, err := auth.List(env.backend)
+		if err != nil {
+			return completionHandlerError(err)
+		}
+
+		completions = make([]string, len(creds))
+		for i, cred := range creds {
+			meta := make([]string, 0, len(cred.Metadata()))
+			for k, v := range cred.Metadata() {
+				meta = append(meta, k+":"+v)
+			}
+			sort.Strings(meta)
+			metaFmt := strings.Join(meta, ",")
+
+			completions[i] = cred.ID().Human() + "\t" + cred.Target() + " " + string(cred.Kind()) + " " + metaFmt
+		}
+
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeBug(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		allIds := env.backend.AllBugsIds()
+		bugExcerpt := make([]*cache.BugExcerpt, len(allIds))
+		for i, id := range allIds {
+			var err error
+			bugExcerpt[i], err = env.backend.ResolveBugExcerpt(id)
+			if err != nil {
+				return completionHandlerError(err)
+			}
+		}
+
+		completions = make([]string, len(allIds))
+		for i, id := range allIds {
+			completions[i] = id.Human() + "\t" + bugExcerpt[i].Title
+		}
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeBugAndLabels(env *Env, addOrRemove bool) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) == 0 {
+			return completeBug(env)(cmd, args, toComplete)
+		}
+
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		b, args, err := _select.ResolveBug(env.backend, args)
+		if err != nil {
+			return completionHandlerError(err)
+		}
+
+		snap := b.Snapshot()
+
+		seenLabels := map[bug.Label]bool{}
+		for _, label := range args {
+			seenLabels[bug.Label(label)] = addOrRemove
+		}
+
+		var labels []bug.Label
+		if addOrRemove {
+			for _, label := range snap.Labels {
+				seenLabels[label] = true
+			}
+
+			allLabels := env.backend.ValidLabels()
+			labels = make([]bug.Label, 0, len(allLabels))
+			for _, label := range allLabels {
+				if !seenLabels[label] {
+					labels = append(labels, label)
+				}
+			}
+		} else {
+			labels = make([]bug.Label, 0, len(snap.Labels))
+			for _, label := range snap.Labels {
+				if seenLabels[label] {
+					labels = append(labels, label)
+				}
+			}
+		}
+
+		completions = make([]string, len(labels))
+		for i, label := range labels {
+			completions[i] = string(label) + "\t" + "Label"
+		}
+
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeFrom(choices []string) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		return choices, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeGitRemote(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		remoteMap, err := env.backend.GetRemotes()
+		if err != nil {
+			return completionHandlerError(err)
+		}
+		completions = make([]string, 0, len(remoteMap))
+		for remote, url := range remoteMap {
+			completions = append(completions, remote+"\t"+"Remote: "+url)
+		}
+		sort.Strings(completions)
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeLabel(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		labels := env.backend.ValidLabels()
+		completions = make([]string, len(labels))
+		for i, label := range labels {
+			completions[i] = string(label) + "\t" + "Label"
+		}
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeLs(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if strings.HasPrefix(toComplete, "status:") {
+			completions = append(completions, "status:open\tOpen bugs")
+			completions = append(completions, "status:closed\tClosed bugs")
+			return completions, cobra.ShellCompDirectiveDefault
+		}
+
+		byPerson := []string{"author:", "participant:", "actor:"}
+		byLabel := []string{"label:", "no:"}
+		needBackend := false
+		for _, key := range append(byPerson, byLabel...) {
+			if strings.HasPrefix(toComplete, key) {
+				needBackend = true
+			}
+		}
+
+		if needBackend {
+			if err := loadBackend(env)(cmd, args); err != nil {
+				return completionHandlerError(err)
+			}
+			defer func() {
+				_ = env.backend.Close()
+			}()
+		}
+
+		for _, key := range byPerson {
+			if !strings.HasPrefix(toComplete, key) {
+				continue
+			}
+			ids := env.backend.AllIdentityIds()
+			completions = make([]string, len(ids))
+			for i, id := range ids {
+				user, err := env.backend.ResolveIdentityExcerpt(id)
+				if err != nil {
+					return completionHandlerError(err)
+				}
+				var handle string
+				if user.Login != "" {
+					handle = user.Login
+				} else {
+					// "author:John Doe" does not work yet, so use the first name.
+					handle = strings.Split(user.Name, " ")[0]
+				}
+				completions[i] = key + handle + "\t" + user.DisplayName()
+			}
+			return completions, cobra.ShellCompDirectiveDefault
+		}
+
+		for _, key := range byLabel {
+			if !strings.HasPrefix(toComplete, key) {
+				continue
+			}
+			labels := env.backend.ValidLabels()
+			completions = make([]string, len(labels))
+			for i, label := range labels {
+				completions[i] = key + string(label)
+			}
+			return completions, cobra.ShellCompDirectiveDefault
+		}
+
+		completions = []string{
+			"actor:\tFilter by actor",
+			"author:\tFilter by author",
+			"label:\tFilter by label",
+			"no:\tExclude bugs by label",
+			"participant:\tFilter by participant",
+			"status:\tFilter by open/close status",
+			"title:\tFilter by title",
+		}
+		return completions, cobra.ShellCompDirectiveNoSpace
+	}
+}
+
+func completeUser(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		ids := env.backend.AllIdentityIds()
+		completions = make([]string, len(ids))
+		for i, id := range ids {
+			user, err := env.backend.ResolveIdentityExcerpt(id)
+			if err != nil {
+				return completionHandlerError(err)
+			}
+			completions[i] = user.Id.Human() + "\t" + user.DisplayName()
+		}
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
+
+func completeUserForQuery(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) (completions []string, directives cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
+		}
+
+		if err := loadBackend(env)(cmd, args); err != nil {
+			return completionHandlerError(err)
+		}
+		defer func() {
+			_ = env.backend.Close()
+		}()
+
+		ids := env.backend.AllIdentityIds()
+		completions = make([]string, len(ids))
+		for i, id := range ids {
+			user, err := env.backend.ResolveIdentityExcerpt(id)
+			if err != nil {
+				return completionHandlerError(err)
+			}
+			var handle string
+			if user.Login != "" {
+				handle = user.Login
+			} else {
+				// "author:John Doe" does not work yet, so use the first name.
+				handle = strings.Split(user.Name, " ")[0]
+			}
+			completions[i] = handle + "\t" + user.DisplayName()
+		}
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}
diff --git a/commands/label.go b/commands/label.go
index d108b089..906974a5 100644
--- a/commands/label.go
+++ b/commands/label.go
@@ -16,6 +16,7 @@ func newLabelCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runLabel(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	cmd.AddCommand(newLabelAddCommand())
diff --git a/commands/label_add.go b/commands/label_add.go
index c60ecfeb..65439a4a 100644
--- a/commands/label_add.go
+++ b/commands/label_add.go
@@ -17,6 +17,7 @@ func newLabelAddCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runLabelAdd(env, args)
 		}),
+		ValidArgsFunction: completeBugAndLabels(env, true),
 	}
 
 	return cmd
diff --git a/commands/label_rm.go b/commands/label_rm.go
index 1cdcd248..3f4e1958 100644
--- a/commands/label_rm.go
+++ b/commands/label_rm.go
@@ -17,6 +17,7 @@ func newLabelRmCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runLabelRm(env, args)
 		}),
+		ValidArgsFunction: completeBugAndLabels(env, false),
 	}
 
 	return cmd
diff --git a/commands/ls.go b/commands/ls.go
index db4145d0..909e25a8 100644
--- a/commands/ls.go
+++ b/commands/ls.go
@@ -56,6 +56,7 @@ git bug ls status:open --by creation "foo bar" baz
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runLs(env, options, args)
 		}),
+		ValidArgsFunction: completeLs(env),
 	}
 
 	flags := cmd.Flags()
@@ -63,26 +64,36 @@ git bug ls status:open --by creation "foo bar" baz
 
 	flags.StringSliceVarP(&options.statusQuery, "status", "s", nil,
 		"Filter by status. Valid values are [open,closed]")
+	cmd.RegisterFlagCompletionFunc("status", completeFrom([]string{"open", "closed"}))
 	flags.StringSliceVarP(&options.authorQuery, "author", "a", nil,
 		"Filter by author")
 	flags.StringSliceVarP(&options.metadataQuery, "metadata", "m", nil,
 		"Filter by metadata. Example: github-url=URL")
+	cmd.RegisterFlagCompletionFunc("author", completeUserForQuery(env))
 	flags.StringSliceVarP(&options.participantQuery, "participant", "p", nil,
 		"Filter by participant")
+	cmd.RegisterFlagCompletionFunc("participant", completeUserForQuery(env))
 	flags.StringSliceVarP(&options.actorQuery, "actor", "A", nil,
 		"Filter by actor")
+	cmd.RegisterFlagCompletionFunc("actor", completeUserForQuery(env))
 	flags.StringSliceVarP(&options.labelQuery, "label", "l", nil,
 		"Filter by label")
+	cmd.RegisterFlagCompletionFunc("label", completeLabel(env))
 	flags.StringSliceVarP(&options.titleQuery, "title", "t", nil,
 		"Filter by title")
 	flags.StringSliceVarP(&options.noQuery, "no", "n", nil,
 		"Filter by absence of something. Valid values are [label]")
+	cmd.RegisterFlagCompletionFunc("no", completeLabel(env))
 	flags.StringVarP(&options.sortBy, "by", "b", "creation",
 		"Sort the results by a characteristic. Valid values are [id,creation,edit]")
+	cmd.RegisterFlagCompletionFunc("by", completeFrom([]string{"id", "creation", "edit"}))
 	flags.StringVarP(&options.sortDirection, "direction", "d", "asc",
 		"Select the sorting direction. Valid values are [asc,desc]")
+	cmd.RegisterFlagCompletionFunc("direction", completeFrom([]string{"asc", "desc"}))
 	flags.StringVarP(&options.outputFormat, "format", "f", "default",
 		"Select the output formatting style. Valid values are [default,plain,json,org-mode]")
+	cmd.RegisterFlagCompletionFunc("format",
+		completeFrom([]string{"default", "plain", "json", "org-mode"}))
 
 	return cmd
 }
diff --git a/commands/pull.go b/commands/pull.go
index f3a31414..29c9f034 100644
--- a/commands/pull.go
+++ b/commands/pull.go
@@ -18,6 +18,7 @@ func newPullCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runPull(env, args)
 		}),
+		ValidArgsFunction: completeGitRemote(env),
 	}
 
 	return cmd
diff --git a/commands/push.go b/commands/push.go
index 9d6ca7df..adba6bef 100644
--- a/commands/push.go
+++ b/commands/push.go
@@ -16,6 +16,7 @@ func newPushCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runPush(env, args)
 		}),
+		ValidArgsFunction: completeGitRemote(env),
 	}
 
 	return cmd
diff --git a/commands/rm.go b/commands/rm.go
index 8205c128..2e1d924d 100644
--- a/commands/rm.go
+++ b/commands/rm.go
@@ -17,6 +17,7 @@ func newRmCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runRm(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	flags := cmd.Flags()
diff --git a/commands/select.go b/commands/select.go
index 34d00a32..f9e6ece7 100644
--- a/commands/select.go
+++ b/commands/select.go
@@ -31,6 +31,7 @@ The complementary command is "git bug deselect" performing the opposite operatio
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runSelect(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	return cmd
diff --git a/commands/show.go b/commands/show.go
index 55140357..16747214 100644
--- a/commands/show.go
+++ b/commands/show.go
@@ -29,13 +29,17 @@ func newShowCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runShow(env, options, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	flags := cmd.Flags()
 	flags.SortFlags = false
 
+	fields := []string{"author", "authorEmail", "createTime", "lastEdit", "humanId",
+		"id", "labels", "shortId", "status", "title", "actors", "participants"}
 	flags.StringVarP(&options.fields, "field", "", "",
-		"Select field to display. Valid values are [author,authorEmail,createTime,lastEdit,humanId,id,labels,shortId,status,title,actors,participants]")
+		"Select field to display. Valid values are ["+strings.Join(fields, ",")+"]")
+	cmd.RegisterFlagCompletionFunc("by", completeFrom(fields))
 	flags.StringVarP(&options.format, "format", "f", "default",
 		"Select the output formatting style. Valid values are [default,json,org-mode]")
 
diff --git a/commands/status.go b/commands/status.go
index c1e45c5f..c3e860b6 100644
--- a/commands/status.go
+++ b/commands/status.go
@@ -15,6 +15,7 @@ func newStatusCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runStatus(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	cmd.AddCommand(newStatusCloseCommand())
diff --git a/commands/title.go b/commands/title.go
index c4293530..f99c6eff 100644
--- a/commands/title.go
+++ b/commands/title.go
@@ -15,6 +15,7 @@ func newTitleCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runTitle(env, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	cmd.AddCommand(newTitleEditCommand())
diff --git a/commands/title_edit.go b/commands/title_edit.go
index 810c5e62..a9e7fe4b 100644
--- a/commands/title_edit.go
+++ b/commands/title_edit.go
@@ -24,6 +24,7 @@ func newTitleEditCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runTitleEdit(env, options, args)
 		}),
+		ValidArgsFunction: completeBug(env),
 	}
 
 	flags := cmd.Flags()
diff --git a/commands/user.go b/commands/user.go
index b6a2e485..0fe3be4d 100644
--- a/commands/user.go
+++ b/commands/user.go
@@ -3,6 +3,7 @@ package commands
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
 
@@ -24,6 +25,7 @@ func newUserCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runUser(env, options, args)
 		}),
+		ValidArgsFunction: completeUser(env),
 	}
 
 	cmd.AddCommand(newUserAdoptCommand())
@@ -33,8 +35,10 @@ func newUserCommand() *cobra.Command {
 	flags := cmd.Flags()
 	flags.SortFlags = false
 
+	fields := []string{"email", "humanId", "id", "lastModification", "lastModificationLamports", "login", "metadata", "name"}
 	flags.StringVarP(&options.fields, "field", "f", "",
-		"Select field to display. Valid values are [email,humanId,id,lastModification,lastModificationLamports,login,metadata,name]")
+		"Select field to display. Valid values are ["+strings.Join(fields, ",")+"]")
+	cmd.RegisterFlagCompletionFunc("field", completeFrom(fields))
 
 	return cmd
 }
diff --git a/commands/user_adopt.go b/commands/user_adopt.go
index 166063ae..afef94ea 100644
--- a/commands/user_adopt.go
+++ b/commands/user_adopt.go
@@ -15,6 +15,7 @@ func newUserAdoptCommand() *cobra.Command {
 		RunE: closeBackend(env, func(cmd *cobra.Command, args []string) error {
 			return runUserAdopt(env, args)
 		}),
+		ValidArgsFunction: completeUser(env),
 	}
 
 	return cmd
diff --git a/commands/user_ls.go b/commands/user_ls.go
index 98800b87..341f0dc1 100644
--- a/commands/user_ls.go
+++ b/commands/user_ls.go
@@ -32,6 +32,7 @@ func newUserLsCommand() *cobra.Command {
 
 	flags.StringVarP(&options.format, "format", "f", "default",
 		"Select the output formatting style. Valid values are [default,json]")
+	cmd.RegisterFlagCompletionFunc("format", completeFrom([]string{"default", "json"}))
 
 	return cmd
 }
diff --git a/misc/bash_completion/git-bug b/misc/bash_completion/git-bug
index 2320c1c0..ab023c71 100644
--- a/misc/bash_completion/git-bug
+++ b/misc/bash_completion/git-bug
@@ -420,7 +420,11 @@ _git-bug_bridge_auth_add-token()
 
     flags+=("--target=")
     two_word_flags+=("--target")
+    flags_with_completion+=("--target")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-t")
+    flags_with_completion+=("-t")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--target")
     local_nonpersistent_flags+=("--target=")
     local_nonpersistent_flags+=("-t")
@@ -432,7 +436,11 @@ _git-bug_bridge_auth_add-token()
     local_nonpersistent_flags+=("-l")
     flags+=("--user=")
     two_word_flags+=("--user")
+    flags_with_completion+=("--user")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-u")
+    flags_with_completion+=("-u")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--user")
     local_nonpersistent_flags+=("--user=")
     local_nonpersistent_flags+=("-u")
@@ -459,6 +467,7 @@ _git-bug_bridge_auth_rm()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -479,6 +488,7 @@ _git-bug_bridge_auth_show()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -527,7 +537,11 @@ _git-bug_bridge_configure()
     local_nonpersistent_flags+=("-n")
     flags+=("--target=")
     two_word_flags+=("--target")
+    flags_with_completion+=("--target")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-t")
+    flags_with_completion+=("-t")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--target")
     local_nonpersistent_flags+=("--target=")
     local_nonpersistent_flags+=("-t")
@@ -608,6 +622,7 @@ _git-bug_bridge_pull()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -628,6 +643,7 @@ _git-bug_bridge_push()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -648,6 +664,7 @@ _git-bug_bridge_rm()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -731,6 +748,7 @@ _git-bug_comment_add()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -787,6 +805,7 @@ _git-bug_comment()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -827,6 +846,7 @@ _git-bug_label_add()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -847,6 +867,7 @@ _git-bug_label_rm()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -869,6 +890,7 @@ _git-bug_label()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -888,13 +910,21 @@ _git-bug_ls()
 
     flags+=("--status=")
     two_word_flags+=("--status")
+    flags_with_completion+=("--status")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-s")
+    flags_with_completion+=("-s")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--status")
     local_nonpersistent_flags+=("--status=")
     local_nonpersistent_flags+=("-s")
     flags+=("--author=")
     two_word_flags+=("--author")
+    flags_with_completion+=("--author")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-a")
+    flags_with_completion+=("-a")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--author")
     local_nonpersistent_flags+=("--author=")
     local_nonpersistent_flags+=("-a")
@@ -906,19 +936,31 @@ _git-bug_ls()
     local_nonpersistent_flags+=("-m")
     flags+=("--participant=")
     two_word_flags+=("--participant")
+    flags_with_completion+=("--participant")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-p")
+    flags_with_completion+=("-p")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--participant")
     local_nonpersistent_flags+=("--participant=")
     local_nonpersistent_flags+=("-p")
     flags+=("--actor=")
     two_word_flags+=("--actor")
+    flags_with_completion+=("--actor")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-A")
+    flags_with_completion+=("-A")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--actor")
     local_nonpersistent_flags+=("--actor=")
     local_nonpersistent_flags+=("-A")
     flags+=("--label=")
     two_word_flags+=("--label")
+    flags_with_completion+=("--label")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-l")
+    flags_with_completion+=("-l")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--label")
     local_nonpersistent_flags+=("--label=")
     local_nonpersistent_flags+=("-l")
@@ -930,31 +972,48 @@ _git-bug_ls()
     local_nonpersistent_flags+=("-t")
     flags+=("--no=")
     two_word_flags+=("--no")
+    flags_with_completion+=("--no")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-n")
+    flags_with_completion+=("-n")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--no")
     local_nonpersistent_flags+=("--no=")
     local_nonpersistent_flags+=("-n")
     flags+=("--by=")
     two_word_flags+=("--by")
+    flags_with_completion+=("--by")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-b")
+    flags_with_completion+=("-b")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--by")
     local_nonpersistent_flags+=("--by=")
     local_nonpersistent_flags+=("-b")
     flags+=("--direction=")
     two_word_flags+=("--direction")
+    flags_with_completion+=("--direction")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-d")
+    flags_with_completion+=("-d")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--direction")
     local_nonpersistent_flags+=("--direction=")
     local_nonpersistent_flags+=("-d")
     flags+=("--format=")
     two_word_flags+=("--format")
+    flags_with_completion+=("--format")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-f")
+    flags_with_completion+=("-f")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--format")
     local_nonpersistent_flags+=("--format=")
     local_nonpersistent_flags+=("-f")
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1015,6 +1074,7 @@ _git-bug_pull()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1035,6 +1095,7 @@ _git-bug_push()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1055,6 +1116,7 @@ _git-bug_rm()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1075,6 +1137,7 @@ _git-bug_select()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1105,6 +1168,7 @@ _git-bug_show()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1167,6 +1231,7 @@ _git-bug_status()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1215,6 +1280,7 @@ _git-bug_title_edit()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1236,6 +1302,7 @@ _git-bug_title()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1256,6 +1323,7 @@ _git-bug_user_adopt()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1315,7 +1383,11 @@ _git-bug_user_ls()
 
     flags+=("--format=")
     two_word_flags+=("--format")
+    flags_with_completion+=("--format")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-f")
+    flags_with_completion+=("-f")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--format")
     local_nonpersistent_flags+=("--format=")
     local_nonpersistent_flags+=("-f")
@@ -1344,13 +1416,18 @@ _git-bug_user()
 
     flags+=("--field=")
     two_word_flags+=("--field")
+    flags_with_completion+=("--field")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     two_word_flags+=("-f")
+    flags_with_completion+=("-f")
+    flags_completion+=("__git-bug_handle_go_custom_completion")
     local_nonpersistent_flags+=("--field")
     local_nonpersistent_flags+=("--field=")
     local_nonpersistent_flags+=("-f")
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }