git: worktree, add Grep() method for git grep

COMPATIBILITY.md

@@ -45,7 +45,7 @@ is supported by go-git.
 | **debugging** |
 | bisect                                | ✖ |
 | blame                                 | ✔ |
-| grep                                  | ✖ |
+| grep                                  | ✔ |
 | **email** ||
 | am                                    | ✖ |
 | apply                                 | ✖ |

options.go

@@ -2,6 +2,7 @@ package git
 
 import (
 	"errors"
+	"regexp"
 
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/plumbing"
@@ -365,3 +366,40 @@ type ListOptions struct {
 type CleanOptions struct {
 	Dir bool
 }
+
+// GrepOptions describes how a grep should be performed.
+type GrepOptions struct {
+	// Pattern is a compiled Regexp object to be matched.
+	Pattern *regexp.Regexp
+	// InvertMatch selects non-matching lines.
+	InvertMatch bool
+	// CommitHash is the hash of the commit from which worktree should be derived.
+	CommitHash plumbing.Hash
+	// ReferenceName is the branch or tag name from which worktree should be derived.
+	ReferenceName plumbing.ReferenceName
+	// PathSpec is a compiled Regexp object of pathspec to use in the matching.
+	PathSpec *regexp.Regexp
+}
+
+var (
+	ErrHashOrReference = errors.New("ambiguous options, only one of CommitHash or ReferenceName can be passed")
+)
+
+// Validate validates the fields and sets the default values.
+func (o *GrepOptions) Validate(w *Worktree) error {
+	if !o.CommitHash.IsZero() && o.ReferenceName != "" {
+		return ErrHashOrReference
+	}
+
+	// If none of CommitHash and ReferenceName are provided, set commit hash of
+	// the repository's head.
+	if o.CommitHash.IsZero() && o.ReferenceName == "" {
+		ref, err := w.r.Head()
+		if err != nil {
+			return err
+		}
+		o.CommitHash = ref.Hash()
+	}
+
+	return nil
+}

worktree.go

@@ -8,6 +8,7 @@ import (
 	stdioutil "io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/plumbing"
@@ -711,6 +712,105 @@ func (w *Worktree) Clean(opts *CleanOptions) error {
 	return nil
 }
 
+// GrepResult is structure of a grep result.
+type GrepResult struct {
+	// FileName is the name of file which contains match.
+	FileName string
+	// LineNumber is the line number of a file at which a match was found.
+	LineNumber int
+	// Content is the content of the file at the matching line.
+	Content string
+	// TreeName is the name of the tree (reference name/commit hash) at
+	// which the match was performed.
+	TreeName string
+}
+
+func (gr GrepResult) String() string {
+	return fmt.Sprintf("%s:%s:%d:%s", gr.TreeName, gr.FileName, gr.LineNumber, gr.Content)
+}
+
+// Grep performs grep on a worktree.
+func (w *Worktree) Grep(opts *GrepOptions) ([]GrepResult, error) {
+	if err := opts.Validate(w); err != nil {
+		return nil, err
+	}
+
+	// Obtain commit hash from options (CommitHash or ReferenceName).
+	var commitHash plumbing.Hash
+	// treeName contains the value of TreeName in GrepResult.
+	var treeName string
+
+	if opts.ReferenceName != "" {
+		ref, err := w.r.Reference(opts.ReferenceName, true)
+		if err != nil {
+			return nil, err
+		}
+		commitHash = ref.Hash()
+		treeName = opts.ReferenceName.String()
+	} else if !opts.CommitHash.IsZero() {
+		commitHash = opts.CommitHash
+		treeName = opts.CommitHash.String()
+	}
+
+	// Obtain a tree from the commit hash and get a tracked files iterator from
+	// the tree.
+	tree, err := w.getTreeFromCommitHash(commitHash)
+	if err != nil {
+		return nil, err
+	}
+	fileiter := tree.Files()
+
+	return findMatchInFiles(fileiter, treeName, opts)
+}
+
+// findMatchInFiles takes a FileIter, worktree name and GrepOptions, and
+// returns a slice of GrepResult containing the result of regex pattern matching
+// in the file content.
+func findMatchInFiles(fileiter *object.FileIter, treeName string, opts *GrepOptions) ([]GrepResult, error) {
+	var results []GrepResult
+
+	// Iterate through the files and look for any matches.
+	err := fileiter.ForEach(func(file *object.File) error {
+		// Check if the file name matches with the pathspec.
+		if opts.PathSpec != nil && !opts.PathSpec.MatchString(file.Name) {
+			return nil
+		}
+
+		content, err := file.Contents()
+		if err != nil {
+			return err
+		}
+
+		// Split the content and make parseable line-by-line.
+		contentByLine := strings.Split(content, "\n")
+		for lineNum, cnt := range contentByLine {
+			addToResult := false
+			// Match the pattern and content.
+			if opts.Pattern != nil && opts.Pattern.MatchString(cnt) {
+				// Add to result only if invert match is not enabled.
+				if !opts.InvertMatch {
+					addToResult = true
+				}
+			} else if opts.InvertMatch {
+				// If matching fails, and invert match is enabled, add to results.
+				addToResult = true
+			}
+
+			if addToResult {
+				results = append(results, GrepResult{
+					FileName:   file.Name,
+					LineNumber: lineNum + 1,
+					Content:    cnt,
+					TreeName:   treeName,
+				})
+			}
+		}
+		return nil
+	})
+
+	return results, err
+}
+
 func rmFileAndDirIfEmpty(fs billy.Filesystem, name string) error {
 	if err := util.RemoveAll(fs, name); err != nil {
 		return err

worktree_test.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"regexp"
 	"runtime"
 
 	"gopkg.in/src-d/go-git.v4/config"
@@ -1317,3 +1318,187 @@ func (s *WorktreeSuite) TestAlternatesRepo(c *C) {
 
 	c.Assert(commit1.String(), Equals, commit2.String())
 }
+
+func (s *WorktreeSuite) TestGrep(c *C) {
+	cases := []struct {
+		name           string
+		options        GrepOptions
+		wantResult     []GrepResult
+		dontWantResult []GrepResult
+		wantError      error
+	}{
+		{
+			name: "basic word match",
+			options: GrepOptions{
+				Pattern: regexp.MustCompile("import"),
+			},
+			wantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+				{
+					FileName:   "vendor/foo.go",
+					LineNumber: 3,
+					Content:    "import \"fmt\"",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+		}, {
+			name: "case insensitive match",
+			options: GrepOptions{
+				Pattern: regexp.MustCompile(`(?i)IMport`),
+			},
+			wantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+				{
+					FileName:   "vendor/foo.go",
+					LineNumber: 3,
+					Content:    "import \"fmt\"",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+		}, {
+			name: "invert match",
+			options: GrepOptions{
+				Pattern:     regexp.MustCompile("import"),
+				InvertMatch: true,
+			},
+			dontWantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+				{
+					FileName:   "vendor/foo.go",
+					LineNumber: 3,
+					Content:    "import \"fmt\"",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+		}, {
+			name: "match at a given commit hash",
+			options: GrepOptions{
+				Pattern:    regexp.MustCompile("The MIT License"),
+				CommitHash: plumbing.NewHash("b029517f6300c2da0f4b651b8642506cd6aaf45d"),
+			},
+			wantResult: []GrepResult{
+				{
+					FileName:   "LICENSE",
+					LineNumber: 1,
+					Content:    "The MIT License (MIT)",
+					TreeName:   "b029517f6300c2da0f4b651b8642506cd6aaf45d",
+				},
+			},
+			dontWantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+		}, {
+			name: "match for a given pathspec",
+			options: GrepOptions{
+				Pattern:  regexp.MustCompile("import"),
+				PathSpec: regexp.MustCompile("go/"),
+			},
+			wantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+			dontWantResult: []GrepResult{
+				{
+					FileName:   "vendor/foo.go",
+					LineNumber: 3,
+					Content:    "import \"fmt\"",
+					TreeName:   "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+				},
+			},
+		}, {
+			name: "match at a given reference name",
+			options: GrepOptions{
+				Pattern:       regexp.MustCompile("import"),
+				ReferenceName: "refs/heads/master",
+			},
+			wantResult: []GrepResult{
+				{
+					FileName:   "go/example.go",
+					LineNumber: 3,
+					Content:    "import (",
+					TreeName:   "refs/heads/master",
+				},
+			},
+		}, {
+			name: "ambiguous options",
+			options: GrepOptions{
+				Pattern:       regexp.MustCompile("import"),
+				CommitHash:    plumbing.NewHash("2d55a722f3c3ecc36da919dfd8b6de38352f3507"),
+				ReferenceName: "somereferencename",
+			},
+			wantError: ErrHashOrReference,
+		},
+	}
+
+	path := fixtures.Basic().ByTag("worktree").One().Worktree().Root()
+	server, err := PlainClone(c.MkDir(), false, &CloneOptions{
+		URL: path,
+	})
+	c.Assert(err, IsNil)
+
+	w, err := server.Worktree()
+	c.Assert(err, IsNil)
+
+	for _, tc := range cases {
+		gr, err := w.Grep(&tc.options)
+		if tc.wantError != nil {
+			c.Assert(err, Equals, tc.wantError)
+		} else {
+			c.Assert(err, IsNil)
+		}
+
+		// Iterate through the results and check if the wanted result is present
+		// in the got result.
+		for _, wantResult := range tc.wantResult {
+			found := false
+			for _, gotResult := range gr {
+				if wantResult == gotResult {
+					found = true
+					break
+				}
+			}
+			if found != true {
+				c.Errorf("unexpected grep results for %q, expected result to contain: %v", tc.name, wantResult)
+			}
+		}
+
+		// Iterate through the results and check if the not wanted result is
+		// present in the got result.
+		for _, dontWantResult := range tc.dontWantResult {
+			found := false
+			for _, gotResult := range gr {
+				if dontWantResult == gotResult {
+					found = true
+					break
+				}
+			}
+			if found != false {
+				c.Errorf("unexpected grep results for %q, expected result to NOT contain: %v", tc.name, dontWantResult)
+			}
+		}
+	}
+}