Complete bug IDs where appropriate

This completes bug IDs in bash and fish.  I haven't gotten this to work in zsh.
In fish, the bug titles are shown as completion label, and can be searched for.
I don't know if/how other shells can show the completion label.
Anyway, everything after the "\t" separator seems to be ignored.

Part of #493

commands/comment.go

@@ -19,6 +19,7 @@ func newCommentCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runComment(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	cmd.AddCommand(newCommentAddCommand())

commands/helper_completion.go

@@ -0,0 +1,49 @@
+package commands
+
+import (
+	"log"
+
+	"github.com/spf13/cobra"
+
+	"github.com/MichaelMure/git-bug/cache"
+	"github.com/MichaelMure/git-bug/query"
+)
+
+type validArgsFunction func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective)
+
+func completeBugs(env *Env) validArgsFunction {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		if err := loadBackend(env)(cmd, args); err != nil {
+			log.Println(err)
+			return nil, cobra.ShellCompDirectiveError
+		}
+		defer func() {
+			err := closeBackend(env)(cmd, args)
+			if err != nil {
+				log.Println(err)
+			}
+		}()
+
+		q := query.NewQuery()
+		allIds, err := env.backend.QueryBugs(q)
+		if err != nil {
+			log.Println(err)
+			return nil, cobra.ShellCompDirectiveError
+		}
+
+		bugExcerpt := make([]*cache.BugExcerpt, len(allIds))
+		for i, id := range allIds {
+			bugExcerpt[i], err = env.backend.ResolveBugExcerpt(id)
+			if err != nil {
+				log.Println(err)
+				return nil, cobra.ShellCompDirectiveError
+			}
+		}
+
+		completions := make([]string, len(allIds))
+		for i, id := range allIds {
+			completions[i] = id.Human() + "\t" + bugExcerpt[i].Title
+		}
+		return completions, cobra.ShellCompDirectiveDefault
+	}
+}

commands/label.go

@@ -17,6 +17,7 @@ func newLabelCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runLabel(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	cmd.AddCommand(newLabelAddCommand())

commands/rm.go

@@ -18,6 +18,7 @@ func newRmCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runRm(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	flags := cmd.Flags()

commands/select.go

@@ -32,6 +32,7 @@ The complementary command is "git bug deselect" performing the opposite operatio
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runSelect(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	return cmd

commands/show.go

@@ -30,6 +30,7 @@ func newShowCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runShow(env, options, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	flags := cmd.Flags()

commands/status.go

@@ -16,6 +16,7 @@ func newStatusCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runStatus(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	cmd.AddCommand(newStatusCloseCommand())

commands/title.go

@@ -16,6 +16,7 @@ func newTitleCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runTitle(env, args)
 		},
+		ValidArgsFunction: completeBugs(env),
 	}
 
 	cmd.AddCommand(newTitleEditCommand())

misc/bash_completion/git-bug

@@ -740,6 +740,7 @@ _git-bug_comment()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -822,6 +823,7 @@ _git-bug_label()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1002,6 +1004,7 @@ _git-bug_rm()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1022,6 +1025,7 @@ _git-bug_select()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1052,6 +1056,7 @@ _git-bug_show()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1114,6 +1119,7 @@ _git-bug_status()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }
 
@@ -1181,6 +1187,7 @@ _git-bug_title()
 
     must_have_one_flag=()
     must_have_one_noun=()
+    has_completion_function=1
     noun_aliases=()
 }