feat(branch): add gs branch squash

.changes/unreleased/Added-20250202-192729.yaml

@@ -0,0 +1,3 @@
+kind: Added
+body: 'branch squash: Squashses all commits in the current branch into a single commit and restacks the upstack branches.'
+time: 2025-02-02T19:27:29.806629-08:00

branch.go

@@ -21,6 +21,7 @@ type branchCmd struct {
 	Delete branchDeleteCmd `cmd:"" aliases:"d,rm" help:"Delete branches"`
 	Fold   branchFoldCmd   `cmd:"" aliases:"fo" help:"Merge a branch into its base"`
 	Split  branchSplitCmd  `cmd:"" aliases:"sp" help:"Split a branch on commits"`
+	Squash branchSquashCmd `cmd:"" aliases:"sq" help:"Squash a branch into one commit"`
 
 	// Mutation
 	Edit    branchEditCmd    `cmd:"" aliases:"e" help:"Edit the commits in a branch"`

branch_checkout.go

@@ -22,7 +22,7 @@ type branchCheckoutCmd struct {
 	checkoutOptions
 
 	Untracked bool   `short:"u" config:"branchCheckout.showUntracked" help:"Show untracked branches if one isn't supplied"`
-	Branch    string `arg:"" optional:"" help:"Name of the branch to delete" predictor:"branches"`
+	Branch    string `arg:"" optional:"" help:"Name of the branch to checkout" predictor:"branches"`
 }
 
 func (*branchCheckoutCmd) Help() string {

branch_squash.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/charmbracelet/log"
+	"go.abhg.dev/gs/internal/git"
+	"go.abhg.dev/gs/internal/spice"
+	"go.abhg.dev/gs/internal/spice/state"
+	"go.abhg.dev/gs/internal/text"
+	"go.abhg.dev/gs/internal/ui"
+)
+
+type branchSquashCmd struct {
+	Message string `short:"m" placeholder:"MSG" help:"Use the given message as the commit message."`
+}
+
+func (*branchSquashCmd) Help() string {
+	return text.Dedent(`
+		Squash all commits in the current branch into a single commit
+		and restack upstack branches.
+	`)
+}
+
+func (cmd *branchSquashCmd) Run(
+	ctx context.Context,
+	log *log.Logger,
+	view ui.View,
+	repo *git.Repository,
+	store *state.Store,
+	svc *spice.Service,
+) error {
+	branchName, err := repo.CurrentBranch(ctx)
+	if err != nil {
+		return fmt.Errorf("get current branch: %w", err)
+	}
+
+	branch, err := svc.LookupBranch(ctx, branchName)
+	if err != nil {
+		return fmt.Errorf("lookup branch %q: %w", branchName, err)
+	}
+
+	if err := svc.VerifyRestacked(ctx, branchName); err != nil {
+		var restackErr *spice.BranchNeedsRestackError
+		if errors.As(err, &restackErr) {
+			return fmt.Errorf("branch %v needs to be restacked before it can be squashed", branchName)
+		}
+		return fmt.Errorf("verify restacked: %w", err)
+	}
+
+	commitMsg := cmd.Message
+
+	if commitMsg == "" {
+		commitMessages, err := repo.CommitMessageRange(ctx, branch.Head.String(), branch.BaseHash.String())
+		if err != nil {
+			return fmt.Errorf("get commit messages: %w", err)
+		}
+		commitMsg = commitMessages[len(commitMessages)-1].String()
+	}
+
+	// Checkout the branch in detached mode
+	if err := (&branchCheckoutCmd{
+		Branch: branchName,
+		checkoutOptions: checkoutOptions{
+			Detach: true,
+		},
+	}).Run(ctx, log, view, repo, store, svc); err != nil {
+		return err
+	}
+
+	// Reset the detached branch to the base commit
+	if err := repo.Reset(ctx, branch.BaseHash.String(), git.ResetOptions{Mode: git.ResetSoft}); err != nil {
+		return err
+	}
+
+	// Commit the changes
+	if err := repo.Commit(ctx, git.CommitRequest{Message: commitMsg}); err != nil {
+		return err
+	}
+
+	// Replace the HEAD ref of `branchName` with the new commit
+	headHash, err := repo.Head(ctx)
+	if err != nil {
+		return err
+	}
+
+	if err := repo.SetRef(ctx, git.SetRefRequest{
+		Ref:  "refs/heads/" + branchName,
+		Hash: headHash,
+	}); err != nil {
+		return err
+	}
+
+	// Check out the original branch
+	if err := repo.Checkout(ctx, branchName); err != nil {
+		return err
+	}
+
+	return (&upstackRestackCmd{}).Run(ctx, log, repo, store, svc)
+}

doc/includes/cli-reference.md

@@ -484,7 +484,7 @@ Use -u/--untracked to show untracked branches in the prompt.
 
 **Arguments**
 
-* `branch`: Name of the branch to delete
+* `branch`: Name of the branch to checkout
 
 **Flags**
 
@@ -642,6 +642,21 @@ For example:
 * `--at=COMMIT:NAME,...`: Commits to split the branch at.
 * `--branch=NAME`: Branch to split commits of.
 
+### gs branch squash
+
+```
+gs branch (b) squash (sq) [flags]
+```
+
+Squash a branch into one commit
+
+Squash all commits in the current branch into a single commit
+and restack upstack branches.
+
+**Flags**
+
+* `-m`, `--message=MSG`: Use the given message as the commit message.
+
 ### gs branch edit
 
 ```

doc/includes/cli-shorthands.md

@@ -10,6 +10,7 @@
 | gs brn | [gs branch rename](/cli/reference.md#gs-branch-rename) |
 | gs bs | [gs branch submit](/cli/reference.md#gs-branch-submit) |
 | gs bsp | [gs branch split](/cli/reference.md#gs-branch-split) |
+| gs bsq | [gs branch squash](/cli/reference.md#gs-branch-squash) |
 | gs btr | [gs branch track](/cli/reference.md#gs-branch-track) |
 | gs buntr | [gs branch untrack](/cli/reference.md#gs-branch-untrack) |
 | gs ca | [gs commit amend](/cli/reference.md#gs-commit-amend) |

testdata/script/branch_squash.txt

@@ -0,0 +1,47 @@
+# Squashing a branch into one commit with 'squash'
+
+as 'Test <[email protected]>'
+at '2024-03-30T14:59:32Z'
+
+cd repo
+git init
+git commit --allow-empty -m 'Initial commit'
+gs repo i
+
+# Create a branch with two commits
+git add feature1.txt
+gs branch create feature-1 -m 'First message in squashed branch'
+git add feature2.txt
+git commit -m 'Second message in squashed branch'
+
+# Create another branch
+git add feature3.txt
+gs branch create feature2 -m 'First message in rebased branch'
+
+git graph --branches
+cmp stdout $WORK/golden/graph-before.txt
+
+# Go back to branch that will be squashed
+gs down
+gs branch squash
+
+git graph --branches
+cmp stdout $WORK/golden/graph.txt
+
+-- repo/dirty.txt --
+Dirty
+-- repo/feature1.txt --
+Feature 1
+-- repo/feature2.txt --
+Feature 2
+-- repo/feature3.txt --
+Feature 3
+-- golden/graph-before.txt --
+* d805cb2 (HEAD -> feature2) First message in rebased branch
+* 0239007 (feature-1) Second message in squashed branch
+* 7ebfd80 First message in squashed branch
+* 9bad92b (main) Initial commit
+-- golden/graph.txt --
+* cbeb99e (feature2) First message in rebased branch
+* 6ca0ea8 (HEAD -> feature-1) First message in squashed branch
+* 9bad92b (main) Initial commit

testdata/script/branch_squash_message.txt

@@ -0,0 +1,47 @@
+# Squashing a branch into one commit with 'squash'
+
+as 'Test <[email protected]>'
+at '2024-03-30T14:59:32Z'
+
+cd repo
+git init
+git commit --allow-empty -m 'Initial commit'
+gs repo i
+
+# Create a branch with two commits
+git add feature1.txt
+gs branch create feature-1 -m 'First message in squashed branch'
+git add feature2.txt
+git commit -m 'Second message in squashed branch'
+
+# Create another branch
+git add feature3.txt
+gs branch create feature2 -m 'First message in rebased branch'
+
+git graph --branches
+cmp stdout $WORK/golden/graph-before.txt
+
+# Go back to branch that will be squashed
+gs down
+gs branch squash -m 'squash feature-1 into one commit'
+
+git graph --branches
+cmp stdout $WORK/golden/graph.txt
+
+-- repo/dirty.txt --
+Dirty
+-- repo/feature1.txt --
+Feature 1
+-- repo/feature2.txt --
+Feature 2
+-- repo/feature3.txt --
+Feature 3
+-- golden/graph-before.txt --
+* d805cb2 (HEAD -> feature2) First message in rebased branch
+* 0239007 (feature-1) Second message in squashed branch
+* 7ebfd80 First message in squashed branch
+* 9bad92b (main) Initial commit
+-- golden/graph.txt --
+* 8323247 (feature2) First message in rebased branch
+* 3267250 (HEAD -> feature-1) squash feature-1 into one commit
+* 9bad92b (main) Initial commit