Update diff-tree wrapper to allow user to use --merge-base

* Updates services/gitdiff/testdata/acedemic-module
  * Changes it to be a bare repo
  * Adds a branch which updates the readme
  * Adds a commit which updates the webpack config
* Updates test cases

services/gitdiff/git_diff_tree.go

@@ -7,6 +7,7 @@ import (
 	"bufio"
 	"context"
 	"fmt"
+	"io"
 	"strings"
 
 	"code.gitea.io/gitea/modules/git"
@@ -29,9 +30,11 @@ type DiffTreeRecord struct {
 	BaseBlobID string
 }
 
-// GetDiffTree returns the list of path of the files that have changed between the two commits
-func GetDiffTree(ctx context.Context, gitRepo *git.Repository, baseSha, headSha string) (*DiffTree, error) {
-	gitDiffTreeRecords, err := runGitDiffTree(ctx, gitRepo, baseSha, headSha)
+// GetDiffTree returns the list of path of the files that have changed between the two commits.
+// If useMergeBase is true, the diff will be calculated using the merge base of the two commits.
+// This is the same behavior as using a three-dot diff in git diff.
+func GetDiffTree(ctx context.Context, gitRepo *git.Repository, useMergeBase bool, baseSha, headSha string) (*DiffTree, error) {
+	gitDiffTreeRecords, err := runGitDiffTree(ctx, gitRepo, useMergeBase, baseSha, headSha)
 	if err != nil {
 		return nil, err
 	}
@@ -41,32 +44,36 @@ func GetDiffTree(ctx context.Context, gitRepo *git.Repository, baseSha, headSha
 	}, nil
 }
 
-func runGitDiffTree(ctx context.Context, gitRepo *git.Repository, baseSha, headSha string) ([]*DiffTreeRecord, error) {
-	baseCommitID, headCommitID, err := validateGitDiffTreeArguments(gitRepo, baseSha, headSha)
+func runGitDiffTree(ctx context.Context, gitRepo *git.Repository, useMergeBase bool, baseSha, headSha string) ([]*DiffTreeRecord, error) {
+	useMergeBase, baseCommitID, headCommitID, err := validateGitDiffTreeArguments(gitRepo, useMergeBase, baseSha, headSha)
 	if err != nil {
 		return nil, err
 	}
 
-	cmd := git.NewCommand(ctx, "diff-tree", "--raw", "-r", "--find-renames").AddDynamicArguments(baseCommitID, headCommitID)
+	cmd := git.NewCommand(ctx, "diff-tree", "--raw", "-r", "--find-renames", "--root")
+	if useMergeBase {
+		cmd.AddArguments("--merge-base")
+	}
+	cmd.AddDynamicArguments(baseCommitID, headCommitID)
 	stdout, _, runErr := cmd.RunStdString(&git.RunOpts{Dir: gitRepo.Path})
 	if runErr != nil {
 		log.Warn("git diff-tree: %v", runErr)
 		return nil, runErr
 	}
 
-	return parseGitDiffTree(stdout)
+	return parseGitDiffTree(strings.NewReader(stdout))
 }
 
-func validateGitDiffTreeArguments(gitRepo *git.Repository, baseSha, headSha string) (string, string, error) {
+func validateGitDiffTreeArguments(gitRepo *git.Repository, useMergeBase bool, baseSha, headSha string) (bool, string, string, error) {
 	// if the head is empty its an error
 	if headSha == "" {
-		return "", "", fmt.Errorf("headSha is empty")
+		return false, "", "", fmt.Errorf("headSha is empty")
 	}
 
 	// if the head commit doesn't exist its and error
 	headCommit, err := gitRepo.GetCommit(headSha)
 	if err != nil {
-		return "", "", fmt.Errorf("failed to get commit headSha: %v", err)
+		return false, "", "", fmt.Errorf("failed to get commit headSha: %v", err)
 	}
 	headCommitID := headCommit.ID.String()
 
@@ -77,30 +84,31 @@ func validateGitDiffTreeArguments(gitRepo *git.Repository, baseSha, headSha stri
 		if headCommit.ParentCount() == 0 {
 			objectFormat, err := gitRepo.GetObjectFormat()
 			if err != nil {
-				return "", "", err
+				return false, "", "", err
 			}
 
-			return objectFormat.EmptyTree().String(), headCommitID, nil
+			// We set use merge base to false because we have no base commit
+			return false, objectFormat.EmptyTree().String(), headCommitID, nil
 		}
 
 		baseCommit, err := headCommit.Parent(0)
 		if err != nil {
-			return "", "", fmt.Errorf("baseSha is '', attempted to use parent of commit %s, got error: %v", headCommit.ID.String(), err)
+			return false, "", "", fmt.Errorf("baseSha is '', attempted to use parent of commit %s, got error: %v", headCommit.ID.String(), err)
 		}
-		return baseCommit.ID.String(), headCommitID, nil
+		return useMergeBase, baseCommit.ID.String(), headCommitID, nil
 	}
 
 	// try and get the base commit
 	baseCommit, err := gitRepo.GetCommit(baseSha)
 	// propagate the error if we couldn't get the base commit
 	if err != nil {
-		return "", "", fmt.Errorf("failed to get base commit %s: %v", baseSha, err)
+		return useMergeBase, "", "", fmt.Errorf("failed to get base commit %s: %v", baseSha, err)
 	}
 
-	return baseCommit.ID.String(), headCommit.ID.String(), nil
+	return useMergeBase, baseCommit.ID.String(), headCommit.ID.String(), nil
 }
 
-func parseGitDiffTree(output string) ([]*DiffTreeRecord, error) {
+func parseGitDiffTree(gitOutput io.Reader) ([]*DiffTreeRecord, error) {
 	/*
 		The output of `git diff-tree --raw -r --find-renames` is of the form:
 
@@ -112,13 +120,9 @@ func parseGitDiffTree(output string) ([]*DiffTreeRecord, error) {
 
 		See: <https://git-scm.com/docs/git-diff-tree#_raw_output_format> for more details
 	*/
-	if output == "" {
-		return []*DiffTreeRecord{}, nil
-	}
-
 	results := make([]*DiffTreeRecord, 0)
 
-	lines := bufio.NewScanner(strings.NewReader(output))
+	lines := bufio.NewScanner(gitOutput)
 	for lines.Scan() {
 		line := lines.Text()
 

services/gitdiff/git_diff_tree_test.go

@@ -4,6 +4,7 @@
 package gitdiff
 
 import (
+	"strings"
 	"testing"
 
 	"code.gitea.io/gitea/models/db"
@@ -15,11 +16,12 @@ import (
 
 func TestGitDiffTree(t *testing.T) {
 	test := []struct {
-		Name     string
-		RepoPath string
-		BaseSha  string
-		HeadSha  string
-		Expected *DiffTree
+		Name         string
+		RepoPath     string
+		BaseSha      string
+		HeadSha      string
+		useMergeBase bool
+		Expected     *DiffTree
 	}{
 		{
 			Name:     "happy path",
@@ -85,6 +87,25 @@ func TestGitDiffTree(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name:         "first commit (no parent), merge base = true",
+			RepoPath:     "./testdata/academic-module",
+			HeadSha:      "07901f79ee86272fa8935f2fe546273adaf02c89",
+			useMergeBase: true,
+			Expected: &DiffTree{
+				Files: []*DiffTreeRecord{
+					{
+						Status:     "added",
+						HeadPath:   "README.md",
+						BasePath:   "README.md",
+						HeadMode:   git.EntryModeBlob,
+						BaseMode:   git.EntryModeNoEntry,
+						HeadBlobID: "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391",
+						BaseBlobID: "0000000000000000000000000000000000000000",
+					},
+				},
+			},
+		},
 		{
 			Name:     "base and head same",
 			RepoPath: "./testdata/academic-module",
@@ -112,14 +133,82 @@ func TestGitDiffTree(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name:         "useMergeBase false",
+			RepoPath:     "./testdata/academic-module",
+			BaseSha:      "819dc756646ffd0730a163b5a8da65b84a6d504e",
+			HeadSha:      "528846b39d8f7e68e8081d586ea3e94be23afa7f", // this commit can be found on the update-readme branch
+			useMergeBase: false,
+			Expected: &DiffTree{
+				Files: []*DiffTreeRecord{
+					{
+						Status:     "modified",
+						HeadPath:   "README.md",
+						BasePath:   "README.md",
+						HeadMode:   git.EntryModeBlob,
+						BaseMode:   git.EntryModeBlob,
+						HeadBlobID: "ca07ea08ae0fa243d6e0a4129843c5a25a02f499",
+						BaseBlobID: "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391",
+					},
+					{
+						Status:     "modified",
+						HeadPath:   "webpack.mix.js",
+						BasePath:   "webpack.mix.js",
+						HeadMode:   git.EntryModeBlob,
+						BaseMode:   git.EntryModeBlob,
+						HeadBlobID: "26825d9cb822e237b600153a26dd1e0e68457196",
+						BaseBlobID: "344e0ca8aa791cc4164fb0ea645f334fd40d00f0",
+					},
+				},
+			},
+		},
+		{
+			Name:         "useMergeBase true",
+			RepoPath:     "./testdata/academic-module",
+			BaseSha:      "819dc756646ffd0730a163b5a8da65b84a6d504e",
+			HeadSha:      "528846b39d8f7e68e8081d586ea3e94be23afa7f", // this commit can be found on the update-readme branch
+			useMergeBase: true,
+			Expected: &DiffTree{
+				Files: []*DiffTreeRecord{
+					{
+						Status:     "modified",
+						HeadPath:   "README.md",
+						BasePath:   "README.md",
+						HeadMode:   git.EntryModeBlob,
+						BaseMode:   git.EntryModeBlob,
+						HeadBlobID: "ca07ea08ae0fa243d6e0a4129843c5a25a02f499",
+						BaseBlobID: "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391",
+					},
+				},
+			},
+		},
+		{
+			Name:         "no base set",
+			RepoPath:     "./testdata/academic-module",
+			HeadSha:      "528846b39d8f7e68e8081d586ea3e94be23afa7f", // this commit can be found on the update-readme branch
+			useMergeBase: false,
+			Expected: &DiffTree{
+				Files: []*DiffTreeRecord{
+					{
+						Status:     "modified",
+						HeadPath:   "README.md",
+						BasePath:   "README.md",
+						HeadMode:   git.EntryModeBlob,
+						BaseMode:   git.EntryModeBlob,
+						HeadBlobID: "ca07ea08ae0fa243d6e0a4129843c5a25a02f499",
+						BaseBlobID: "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391",
+					},
+				},
+			},
+		},
 	}
 
 	for _, tt := range test {
 		t.Run(tt.Name, func(t *testing.T) {
 			gitRepo, err := git.OpenRepository(git.DefaultContext, tt.RepoPath)
 			assert.NoError(t, err)
 
-			diffPaths, err := GetDiffTree(db.DefaultContext, gitRepo, tt.BaseSha, tt.HeadSha)
+			diffPaths, err := GetDiffTree(db.DefaultContext, gitRepo, tt.useMergeBase, tt.BaseSha, tt.HeadSha)
 			require.NoError(t, err)
 
 			assert.Equal(t, tt.Expected, diffPaths)
@@ -158,7 +247,7 @@ func TestGitDiffTreeErrors(t *testing.T) {
 			gitRepo, err := git.OpenRepository(git.DefaultContext, tt.RepoPath)
 			assert.NoError(t, err)
 
-			diffPaths, err := GetDiffTree(db.DefaultContext, gitRepo, tt.BaseSha, tt.HeadSha)
+			diffPaths, err := GetDiffTree(db.DefaultContext, gitRepo, true, tt.BaseSha, tt.HeadSha)
 			assert.Error(t, err)
 			assert.Nil(t, diffPaths)
 		})
@@ -310,7 +399,7 @@ func TestParseGitDiffTree(t *testing.T) {
 
 	for _, tt := range test {
 		t.Run(tt.Name, func(t *testing.T) {
-			entries, err := parseGitDiffTree(tt.GitOutput)
+			entries, err := parseGitDiffTree(strings.NewReader(tt.GitOutput))
 			assert.NoError(t, err)
 			assert.Equal(t, tt.Expected, entries)
 		})

services/gitdiff/testdata/academic-module/config

@@ -1,7 +1,7 @@
 [core]
 	repositoryformatversion = 0
 	filemode = true
-	bare = false
+	bare = true
 	logallrefupdates = true
 	ignorecase = true
 	precomposeunicode = true

services/gitdiff/testdata/academic-module/logs/HEAD

@@ -1 +1,2 @@
 0000000000000000000000000000000000000000 bd7063cc7c04689c4d082183d32a604ed27a24f9 Lunny Xiao <[email protected]> 1574829684 +0800	clone: from https://try.gitea.io/shemgp-aiias/academic-module
+0000000000000000000000000000000000000000 819dc756646ffd0730a163b5a8da65b84a6d504e Alexander McRae <[email protected]> 1737998543 -0800	push

services/gitdiff/testdata/academic-module/logs/refs/heads/master

@@ -1 +1,2 @@
 0000000000000000000000000000000000000000 bd7063cc7c04689c4d082183d32a604ed27a24f9 Lunny Xiao <[email protected]> 1574829684 +0800	clone: from https://try.gitea.io/shemgp-aiias/academic-module
+bd7063cc7c04689c4d082183d32a604ed27a24f9 819dc756646ffd0730a163b5a8da65b84a6d504e Alexander McRae <[email protected]> 1737998543 -0800	push

services/gitdiff/testdata/academic-module/logs/refs/heads/update-readme

@@ -0,0 +1 @@
+0000000000000000000000000000000000000000 528846b39d8f7e68e8081d586ea3e94be23afa7f Alexander McRae <[email protected]> 1737998161 -0800	push

services/gitdiff/testdata/academic-module/objects/34/4e0ca8aa791cc4164fb0ea645f334fd40d00f0

@@ -0,0 +1,2 @@
+x
���J!���)�N���D�E��Wg�qYus�C�{*��	A���gfZ��w76E*�;<AƷ�g|5�\p*���Ň���C0��H�i�ꊰ���z;�r\)]��	���\k�w�B�xt>Gn��W��g���@�K�m�Z����5���Hu)���r�ԓ�RϪ�oXc�'��y�-'���S<�q�႙*��������#
+)᣷�~�r�}
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services/gitdiff/testdata/academic-module/refs/heads/master

@@ -1 +1 @@
-bd7063cc7c04689c4d082183d32a604ed27a24f9
+819dc756646ffd0730a163b5a8da65b84a6d504e

services/gitdiff/testdata/academic-module/refs/heads/update-readme

@@ -0,0 +1 @@
+528846b39d8f7e68e8081d586ea3e94be23afa7f