feat: only emit changed files with git walker

If the modified time has not changed when compared with the git index we do not emit the file for processing.

This allows users to introduce treefmt to a repository without suffering an initial large formatting commit.

Instead, files can be formatted incrementally as they are changed.

Closes #311

Signed-off-by: Brian McGee <brian@bmcgee.ie>

cache/cache.go

@@ -12,7 +12,7 @@ import (
 	"git.numtide.com/numtide/treefmt/stats"
 
 	"git.numtide.com/numtide/treefmt/format"
-	"git.numtide.com/numtide/treefmt/walk"
+	"git.numtide.com/numtide/treefmt/walker"
 
 	"github.com/charmbracelet/log"
 
@@ -187,7 +187,7 @@ func putEntry(bucket *bolt.Bucket, path string, entry *Entry) error {
 
 // ChangeSet is used to walk a filesystem, starting at root, and outputting any new or changed paths using pathsCh.
 // It determines if a path is new or has changed by comparing against cache entries.
-func ChangeSet(ctx context.Context, walker walk.Walker, filesCh chan<- *walk.File) error {
+func ChangeSet(ctx context.Context, wk walker.Walker, filesCh chan<- *walker.File) error {
 	start := time.Now()
 
 	defer func() {
@@ -205,7 +205,7 @@ func ChangeSet(ctx context.Context, walker walk.Walker, filesCh chan<- *walk.Fil
 		}
 	}()
 
-	return walker.Walk(ctx, func(file *walk.File, err error) error {
+	return wk.Walk(ctx, func(file *walker.File, err error) error {
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
@@ -264,7 +264,7 @@ func ChangeSet(ctx context.Context, walker walk.Walker, filesCh chan<- *walk.Fil
 }
 
 // Update is used to record updated cache information for the specified list of paths.
-func Update(files []*walk.File) error {
+func Update(files []*walker.File) error {
 	start := time.Now()
 	defer func() {
 		logger.Debugf("finished processing %v paths in %v", len(files), time.Since(start))

cli/cli.go

@@ -6,7 +6,7 @@ import (
 	"github.com/gobwas/glob"
 
 	"git.numtide.com/numtide/treefmt/format"
-	"git.numtide.com/numtide/treefmt/walk"
+	"git.numtide.com/numtide/treefmt/walker"
 	"github.com/alecthomas/kong"
 	"github.com/charmbracelet/log"
 )
@@ -25,10 +25,11 @@ type Format struct {
 	Formatters            []string           `short:"f" help:"Specify formatters to apply. Defaults to all formatters."`
 	TreeRoot              string             `type:"existingdir" xor:"tree-root" help:"The root directory from which treefmt will start walking the filesystem (defaults to the directory containing the config file)."`
 	TreeRootFile          string             `type:"string" xor:"tree-root" help:"File to search for to find the project root (if --tree-root is not passed)."`
-	Walk                  walk.Type          `enum:"auto,git,filesystem" default:"auto" help:"The method used to traverse the files within --tree-root. Currently supports 'auto', 'git' or 'filesystem'."`
-	Verbosity             int                `name:"verbose" short:"v" type:"counter" default:"0" env:"LOG_LEVEL" help:"Set the verbosity of logs e.g. -vv."`
-	Version               bool               `name:"version" short:"V" help:"Print version."`
-	Init                  bool               `name:"init" short:"i" help:"Create a new treefmt.toml."`
+	Walk                  walker.Type        `enum:"auto,git,filesystem" default:"auto" help:"The method used to traverse the files within --tree-root. Currently supports 'auto', 'git' or 'filesystem'."`
+
+	Verbosity int  `name:"verbose" short:"v" type:"counter" default:"0" env:"LOG_LEVEL" help:"Set the verbosity of logs e.g. -vv."`
+	Version   bool `name:"version" short:"V" help:"Print version."`
+	Init      bool `name:"init" short:"i" help:"Create a new treefmt.toml."`
 
 	OnUnmatched log.Level `name:"on-unmatched" short:"u" default:"warn" help:"Log paths that did not match any formatters at the specified log level, with fatal exiting the process with an error. Possible values are <debug|info|warn|error|fatal>."`
 
@@ -40,9 +41,9 @@ type Format struct {
 	formatters     map[string]*format.Formatter
 	globalExcludes []glob.Glob
 
-	filesCh     chan *walk.File
-	formattedCh chan *walk.File
-	processedCh chan *walk.File
+	fileCh      chan *walker.File
+	formattedCh chan *walker.File
+	processedCh chan *walker.File
 }
 
 func (f *Format) configureLogging() {

cli/format.go

@@ -18,7 +18,7 @@ import (
 
 	"git.numtide.com/numtide/treefmt/cache"
 	"git.numtide.com/numtide/treefmt/config"
-	"git.numtide.com/numtide/treefmt/walk"
+	"git.numtide.com/numtide/treefmt/walker"
 
 	"github.com/charmbracelet/log"
 	"golang.org/x/sync/errgroup"
@@ -147,13 +147,13 @@ func (f *Format) Run() (err error) {
 
 	// create a channel for files needing to be processed
 	// we use a multiple of batch size here as a rudimentary concurrency optimization based on the host machine
-	f.filesCh = make(chan *walk.File, BatchSize*runtime.NumCPU())
+	f.fileCh = make(chan *walker.File, BatchSize*runtime.NumCPU())
 
 	// create a channel for files that have been formatted
-	f.formattedCh = make(chan *walk.File, cap(f.filesCh))
+	f.formattedCh = make(chan *walker.File, cap(f.fileCh))
 
 	// create a channel for files that have been processed
-	f.processedCh = make(chan *walk.File, cap(f.filesCh))
+	f.processedCh = make(chan *walker.File, cap(f.fileCh))
 
 	// start concurrent processing tasks in reverse order
 	eg.Go(f.updateCache(ctx))
@@ -168,14 +168,14 @@ func (f *Format) Run() (err error) {
 func (f *Format) walkFilesystem(ctx context.Context) func() error {
 	return func() error {
 		eg, ctx := errgroup.WithContext(ctx)
-		pathsCh := make(chan string, BatchSize)
+		pathCh := make(chan string, BatchSize)
 
 		// By default, we use the cli arg, but if the stdin flag has been set we force a filesystem walk
 		// since we will only be processing one file from a temp directory
 		walkerType := f.Walk
 
 		if f.Stdin {
-			walkerType = walk.Filesystem
+			walkerType = walker.Filesystem
 
 			// check we have only received one path arg which we use for the file extension / matching to formatters
 			if len(f.Paths) != 1 {
@@ -197,15 +197,15 @@ func (f *Format) walkFilesystem(ctx context.Context) func() error {
 		}
 
 		walkPaths := func() error {
-			defer close(pathsCh)
+			defer close(pathCh)
 
 			var idx int
 			for idx < len(f.Paths) {
 				select {
 				case <-ctx.Done():
 					return ctx.Err()
 				default:
-					pathsCh <- f.Paths[idx]
+					pathCh <- f.Paths[idx]
 					idx += 1
 				}
 			}
@@ -217,37 +217,37 @@ func (f *Format) walkFilesystem(ctx context.Context) func() error {
 			eg.Go(walkPaths)
 		} else {
 			// no explicit paths to process, so we only need to process root
-			pathsCh <- f.TreeRoot
-			close(pathsCh)
+			pathCh <- f.TreeRoot
+			close(pathCh)
 		}
 
 		// create a filesystem walker
-		walker, err := walk.New(walkerType, f.TreeRoot, pathsCh)
+		wk, err := walker.New(walkerType, f.TreeRoot, f.NoCache, pathCh)
 		if err != nil {
 			return fmt.Errorf("failed to create walker: %w", err)
 		}
 
-		// close the files channel when we're done walking the file system
-		defer close(f.filesCh)
+		// close the file channel when we're done walking the file system
+		defer close(f.fileCh)
 
 		// if no cache has been configured, or we are processing from stdin, we invoke the walker directly
 		if f.NoCache || f.Stdin {
-			return walker.Walk(ctx, func(file *walk.File, err error) error {
+			return wk.Walk(ctx, func(file *walker.File, err error) error {
 				select {
 				case <-ctx.Done():
 					return ctx.Err()
 				default:
 					stats.Add(stats.Traversed, 1)
 					stats.Add(stats.Emitted, 1)
-					f.filesCh <- file
+					f.fileCh <- file
 					return nil
 				}
 			})
 		}
 
 		// otherwise we pass the walker to the cache and have it generate files for processing based on whether or not
 		// they have been added/changed since the last invocation
-		if err = cache.ChangeSet(ctx, walker, f.filesCh); err != nil {
+		if err = cache.ChangeSet(ctx, wk, f.fileCh); err != nil {
 			return fmt.Errorf("failed to generate change set: %w", err)
 		}
 		return nil
@@ -319,7 +319,7 @@ func (f *Format) applyFormatters(ctx context.Context) func() error {
 		}()
 
 		// iterate the files channel
-		for file := range f.filesCh {
+		for file := range f.fileCh {
 
 			// first check if this file has been globally excluded
 			if format.PathMatches(file.RelPath, f.globalExcludes) {
@@ -419,7 +419,7 @@ func (f *Format) detectFormatted(ctx context.Context) func() error {
 func (f *Format) updateCache(ctx context.Context) func() error {
 	return func() error {
 		// used to batch updates for more efficient txs
-		batch := make([]*walk.File, 0, BatchSize)
+		batch := make([]*walker.File, 0, BatchSize)
 
 		// apply a batch
 		processBatch := func() error {

format/formatter.go

@@ -8,7 +8,7 @@ import (
 	"os/exec"
 	"time"
 
-	"git.numtide.com/numtide/treefmt/walk"
+	"git.numtide.com/numtide/treefmt/walker"
 
 	"git.numtide.com/numtide/treefmt/config"
 
@@ -89,7 +89,7 @@ func (f *Formatter) Apply(ctx context.Context, tasks []*Task) error {
 
 // Wants is used to test if a Formatter wants a path based on it's configured Includes and Excludes patterns.
 // Returns true if the Formatter should be applied to path, false otherwise.
-func (f *Formatter) Wants(file *walk.File) bool {
+func (f *Formatter) Wants(file *walker.File) bool {
 	match := !PathMatches(file.RelPath, f.excludes) && PathMatches(file.RelPath, f.includes)
 	if match {
 		f.log.Debugf("match: %v", file)

format/task.go

@@ -4,16 +4,16 @@ import (
 	"cmp"
 	"slices"
 
-	"git.numtide.com/numtide/treefmt/walk"
+	"git.numtide.com/numtide/treefmt/walker"
 )
 
 type Task struct {
-	File       *walk.File
+	File       *walker.File
 	Formatters []*Formatter
 	BatchKey   string
 }
 
-func NewTask(file *walk.File, formatters []*Formatter) Task {
+func NewTask(file *walker.File, formatters []*Formatter) Task {
 	// sort by priority in ascending order
 	slices.SortFunc(formatters, func(a, b *Formatter) int {
 		priorityA := a.Priority()

walk/filesystem.go → walker/filesystem.go

@@ -1,4 +1,4 @@
-package walk
+package walker
 
 import (
 	"context"

walk/filesystem_test.go → walker/filesystem_test.go

@@ -1,4 +1,4 @@
-package walk
+package walker
 
 import (
 	"context"

walk/git.go → walker/git.go

@@ -1,21 +1,26 @@
-package walk
+package walker
 
 import (
 	"context"
 	"fmt"
 	"io/fs"
 	"os"
 	"path/filepath"
+	"time"
+
+	"github.com/go-git/go-git/v5/plumbing/format/index"
 
 	"github.com/charmbracelet/log"
 
 	"github.com/go-git/go-git/v5"
 )
 
 type gitWalker struct {
-	root          string
-	paths         chan string
-	repo          *git.Repository
+	root  string
+	paths chan string
+	repo  *git.Repository
+
+	noCache       bool
 	relPathOffset int
 }
 
@@ -39,7 +44,20 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 	}
 
 	// cache in-memory whether a path is present in the git index
-	var cache map[string]bool
+	var cache map[string]*index.Entry
+
+	// by default, we only emit files if they have changes when compared with the git index
+	emitFile := func(entry *index.Entry, info os.FileInfo) bool {
+		// mod time comparison is done with EPOCH (second) precision as per the POSIX spec
+		return entry.ModifiedAt.Truncate(time.Second) != info.ModTime().Truncate(time.Second)
+	}
+
+	if g.noCache {
+		// emit all files in the index
+		emitFile = func(entry *index.Entry, info os.FileInfo) bool {
+			return true
+		}
+	}
 
 	for path := range g.paths {
 
@@ -63,6 +81,11 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 						return fmt.Errorf("failed to stat %s: %w", path, err)
 					}
 
+					// skip processing if the file hasn't changed
+					if !emitFile(entry, info) {
+						continue
+					}
+
 					// determine a relative path
 					relPath, err := g.relPath(path)
 					if err != nil {
@@ -83,11 +106,11 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 			continue
 		}
 
-		// otherwise we ensure the git index entries are cached and then check if they are in the git index
+		// otherwise we ensure the git index entries are cached and then check if the path is in the git index
 		if cache == nil {
-			cache = make(map[string]bool)
+			cache = make(map[string]*index.Entry)
 			for _, entry := range idx.Entries {
-				cache[entry.Name] = true
+				cache[entry.Name] = entry
 			}
 		}
 
@@ -103,7 +126,8 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 		}
 
 		return filepath.Walk(path, func(path string, info fs.FileInfo, _ error) error {
-			if info.IsDir() {
+			// ignore directories and symlinks
+			if info.IsDir() || info.Mode()&os.ModeSymlink == os.ModeSymlink {
 				return nil
 			}
 
@@ -112,9 +136,12 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 				return fmt.Errorf("failed to determine a relative path for %s: %w", path, err)
 			}
 
-			if _, ok := cache[relPath]; !ok {
+			if entry, ok := cache[relPath]; !ok {
 				log.Debugf("path %v not found in git index, skipping", path)
 				return nil
+			} else if !emitFile(entry, info) {
+				log.Debugf("path %v has not changed, skipping", path)
+				return nil
 			}
 
 			file := File{
@@ -130,7 +157,11 @@ func (g gitWalker) Walk(ctx context.Context, fn WalkFunc) error {
 	return nil
 }
 
-func NewGit(root string, paths chan string) (Walker, error) {
+func NewGit(
+	root string,
+	noCache bool,
+	paths chan string,
+) (Walker, error) {
 	repo, err := git.PlainOpen(root)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open git repo: %w", err)
@@ -139,6 +170,7 @@ func NewGit(root string, paths chan string) (Walker, error) {
 		root:          root,
 		paths:         paths,
 		repo:          repo,
+		noCache:       noCache,
 		relPathOffset: len(root) + 1,
 	}, nil
 }