feat: add mr diff command (#281)

* feat: add mr diff command

* fix mr docs

* add tests

* linting

* fix test

commands/mr/approvers/mr_approvers.go

@@ -16,7 +16,7 @@ import (
 
 func NewCmdApprovers(f *cmdutils.Factory) *cobra.Command {
 	var mrApproversCmd = &cobra.Command{
-		Use:     "approvers <id> [flags]",
+		Use:     "approvers [<id> | <branch>] [flags]",
 		Short:   `List merge request eligible approvers`,
 		Long:    ``,
 		Aliases: []string{},

commands/mr/checkout/mr_checkout.go

@@ -24,7 +24,7 @@ var (
 
 func NewCmdCheckout(f *cmdutils.Factory) *cobra.Command {
 	var mrCheckoutCmd = &cobra.Command{
-		Use:   "checkout <mr-id>",
+		Use:   "checkout <id>",
 		Short: "Checkout to an open merge request",
 		Long:  ``,
 		Args:  cobra.ExactArgs(1),

commands/mr/close/mr_close.go

@@ -15,7 +15,7 @@ import (
 
 func NewCmdClose(f *cmdutils.Factory) *cobra.Command {
 	var mrCloseCmd = &cobra.Command{
-		Use:   "close <id>",
+		Use:   "close [<id> | <branch>]",
 		Short: `Close merge requests`,
 		Long:  ``,
 		Args:  cobra.MaximumNArgs(1),

commands/mr/delete/mr_delete.go

@@ -13,7 +13,7 @@ import (
 
 func NewCmdDelete(f *cmdutils.Factory) *cobra.Command {
 	var mrDeleteCmd = &cobra.Command{
-		Use:     "delete <id>",
+		Use:     "delete [<id> | <branch>]",
 		Short:   `Delete merge requests`,
 		Long:    ``,
 		Aliases: []string{"del"},

commands/mr/delete/mr_delete_test.go

@@ -103,7 +103,7 @@ hosts:
 			name:    "delete no args",
 			wantErr: true,
 			assertFunc: func(t *testing.T, out string) {
-				assert.Contains(t, out, "no open merge request availabe for \"master\"")
+				assert.Contains(t, out, "no open merge request available for \"master\"")
 			},
 		},
 	}

commands/mr/diff/diff.go

@@ -0,0 +1,164 @@
+// adapted from https://github.com/cli/cli/blob/trunk/pkg/cmd/pr/diff/diff.go
+package diff
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"syscall"
+
+	"github.com/profclems/glab/commands/cmdutils"
+	"github.com/profclems/glab/commands/mr/mrutils"
+	"github.com/profclems/glab/internal/utils"
+	"github.com/xanzy/go-gitlab"
+
+	"github.com/spf13/cobra"
+)
+
+type DiffOptions struct {
+	factory *cmdutils.Factory
+	IO      *utils.IOStreams
+
+	Args     []string
+	UseColor string
+}
+
+func NewCmdDiff(f *cmdutils.Factory, runF func(*DiffOptions) error) *cobra.Command {
+	opts := &DiffOptions{
+		factory: f,
+		IO:      f.IO,
+	}
+
+	cmd := &cobra.Command{
+		Use:   "diff [<id> | <branch>]",
+		Short: "View changes in a merge request",
+		Args:  cobra.MaximumNArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+
+			if repoOverride, _ := cmd.Flags().GetString("repo"); repoOverride != "" && len(args) == 0 {
+				return &cmdutils.FlagError{Err: errors.New("argument required when using the --repo flag")}
+			}
+
+			if len(args) > 0 {
+				opts.Args = args
+			}
+
+			if !validColorFlag(opts.UseColor) {
+				return &cmdutils.FlagError{Err: fmt.Errorf("did not understand color: %q. Expected one of always, never, or auto", opts.UseColor)}
+			}
+
+			if opts.UseColor == "auto" && !opts.IO.IsaTTY {
+				opts.UseColor = "never"
+			}
+
+			if runF != nil {
+				return runF(opts)
+			}
+			return diffRun(opts)
+		},
+	}
+
+	cmd.Flags().StringVar(&opts.UseColor, "color", "auto", "Use color in diff output: {always|never|auto}")
+
+	return cmd
+}
+
+func diffRun(opts *DiffOptions) error {
+	apiClient, err := opts.factory.HttpClient()
+	if err != nil {
+		return err
+	}
+	mr, baseRepo, err := mrutils.MRFromArgs(opts.factory, opts.Args)
+	if err != nil {
+		return err
+	}
+
+	diffs, _, err := apiClient.MergeRequests.GetMergeRequestDiffVersions(baseRepo.FullName(), mr.IID, &gitlab.GetMergeRequestDiffVersionsOptions{})
+	if err != nil {
+		return fmt.Errorf("could not find merge request diffs: %w", err)
+	}
+
+	diffOut := &bytes.Buffer{}
+	for _, diff := range diffs {
+		// the diffs are not included in the GetMergeRequestDiffVersions so we query for each diff version
+		diffVersion, _, err := apiClient.MergeRequests.GetSingleMergeRequestDiffVersion(baseRepo.FullName(), mr.IID, diff.ID)
+		if err != nil {
+			return fmt.Errorf("could not find merge request diff: %w", err)
+		}
+		for _, diffLine := range diffVersion.Diffs {
+			if diffLine.RenamedFile {
+				diffOut.WriteString("-" + diffLine.OldPath + "\n")
+			}
+			if diffLine.NewFile || diffLine.RenamedFile {
+				diffOut.WriteString("+" + diffLine.NewPath + "\n")
+			} else {
+				diffOut.WriteString(diffLine.OldPath + "\n")
+			}
+
+			diffOut.WriteString(diffLine.Diff)
+		}
+	}
+
+	defer diffOut.Reset()
+
+	err = opts.IO.StartPager()
+	if err != nil {
+		return err
+	}
+	defer opts.IO.StopPager()
+
+	if opts.UseColor == "never" {
+		_, err = io.Copy(opts.IO.StdOut, diffOut)
+		if errors.Is(err, syscall.EPIPE) {
+			return nil
+		}
+		return err
+	}
+
+	diffLines := bufio.NewScanner(diffOut)
+	for diffLines.Scan() {
+		diffLine := diffLines.Text()
+		switch {
+		case isHeaderLine(diffLine):
+			fmt.Fprintf(opts.IO.StdOut, "\x1b[1;38m%s\x1b[m\n", diffLine)
+		case isAdditionLine(diffLine):
+			fmt.Fprintf(opts.IO.StdOut, "\x1b[32m%s\x1b[m\n", diffLine)
+		case isRemovalLine(diffLine):
+			fmt.Fprintf(opts.IO.StdOut, "\x1b[31m%s\x1b[m\n", diffLine)
+		default:
+			fmt.Fprintln(opts.IO.StdOut, diffLine)
+		}
+	}
+
+	if err := diffLines.Err(); err != nil {
+		return fmt.Errorf("error reading merge request diff: %w", err)
+	}
+
+	return nil
+}
+
+var diffHeaderPrefixes = []string{"+++", "---", "diff", "index"}
+
+func isHeaderLine(dl string) bool {
+	for _, p := range diffHeaderPrefixes {
+		if strings.HasPrefix(dl, p) {
+			return true
+		}
+	}
+	return false
+}
+
+func isAdditionLine(dl string) bool {
+	return strings.HasPrefix(dl, "+")
+}
+
+func isRemovalLine(dl string) bool {
+	return strings.HasPrefix(dl, "-")
+}
+
+func validColorFlag(c string) bool {
+	return c == "auto" || c == "always" || c == "never"
+}