[CHORE] Drop go-git support

See https://codeberg.org/forgejo/discussions/issues/164 for the
rationale and discussion of this change.

Everything related to the `go-git` dependency is dropped (Only a single
instance is left in a test file to test for an XSS, it requires crafting
an commit that Git itself refuses to craft). `_gogit` files have
been removed entirely, `go:build: !gogit` is removed, `XXX_nogogit.go` files
either have been renamed or had their code being merged into the
`XXX.go` file.

modules/git/repo_language_stats.go

@@ -4,8 +4,17 @@
 package git
 
 import (
+	"bytes"
+	"cmp"
+	"io"
 	"strings"
 	"unicode"
+
+	"code.gitea.io/gitea/modules/analyze"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
+
+	"github.com/go-enry/go-enry/v2"
 )
 
 const (
@@ -46,3 +55,194 @@ func mergeLanguageStats(stats map[string]int64) map[string]int64 {
 	}
 	return res
 }
+
+// GetLanguageStats calculates language stats for git repository at specified commit
+func (repo *Repository) GetLanguageStats(commitID string) (map[string]int64, error) {
+	// We will feed the commit IDs in order into cat-file --batch, followed by blobs as necessary.
+	// so let's create a batch stdin and stdout
+	batchStdinWriter, batchReader, cancel := repo.CatFileBatch(repo.Ctx)
+	defer cancel()
+
+	writeID := func(id string) error {
+		_, err := batchStdinWriter.Write([]byte(id + "\n"))
+		return err
+	}
+
+	if err := writeID(commitID); err != nil {
+		return nil, err
+	}
+	shaBytes, typ, size, err := ReadBatchLine(batchReader)
+	if typ != "commit" {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, ErrNotExist{commitID, ""}
+	}
+
+	sha, err := NewIDFromString(string(shaBytes))
+	if err != nil {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, ErrNotExist{commitID, ""}
+	}
+
+	commit, err := CommitFromReader(repo, sha, io.LimitReader(batchReader, size))
+	if err != nil {
+		log.Debug("Unable to get commit for: %s. Err: %v", commitID, err)
+		return nil, err
+	}
+	if _, err = batchReader.Discard(1); err != nil {
+		return nil, err
+	}
+
+	tree := commit.Tree
+
+	entries, err := tree.ListEntriesRecursiveWithSize()
+	if err != nil {
+		return nil, err
+	}
+
+	checker, err := repo.GitAttributeChecker(commitID, LinguistAttributes...)
+	if err != nil {
+		return nil, err
+	}
+	defer checker.Close()
+
+	contentBuf := bytes.Buffer{}
+	var content []byte
+
+	// sizes contains the current calculated size of all files by language
+	sizes := make(map[string]int64)
+	// by default we will only count the sizes of programming languages or markup languages
+	// unless they are explicitly set using linguist-language
+	includedLanguage := map[string]bool{}
+	// or if there's only one language in the repository
+	firstExcludedLanguage := ""
+	firstExcludedLanguageSize := int64(0)
+
+	isTrue := func(v optional.Option[bool]) bool {
+		return v.ValueOrDefault(false)
+	}
+	isFalse := func(v optional.Option[bool]) bool {
+		return !v.ValueOrDefault(true)
+	}
+
+	for _, f := range entries {
+		select {
+		case <-repo.Ctx.Done():
+			return sizes, repo.Ctx.Err()
+		default:
+		}
+
+		contentBuf.Reset()
+		content = contentBuf.Bytes()
+
+		if f.Size() == 0 {
+			continue
+		}
+
+		isVendored := optional.None[bool]()
+		isGenerated := optional.None[bool]()
+		isDocumentation := optional.None[bool]()
+		isDetectable := optional.None[bool]()
+
+		attrs, err := checker.CheckPath(f.Name())
+		if err == nil {
+			isVendored = attrs["linguist-vendored"].Bool()
+			isGenerated = attrs["linguist-generated"].Bool()
+			isDocumentation = attrs["linguist-documentation"].Bool()
+			isDetectable = attrs["linguist-detectable"].Bool()
+			if language := cmp.Or(
+				attrs["linguist-language"].String(),
+				attrs["gitlab-language"].Prefix(),
+			); language != "" {
+				// group languages, such as Pug -> HTML; SCSS -> CSS
+				group := enry.GetLanguageGroup(language)
+				if len(group) != 0 {
+					language = group
+				}
+
+				// this language will always be added to the size
+				sizes[language] += f.Size()
+				continue
+			}
+		}
+
+		if isFalse(isDetectable) || isTrue(isVendored) || isTrue(isDocumentation) ||
+			(!isFalse(isVendored) && analyze.IsVendor(f.Name())) ||
+			enry.IsDotFile(f.Name()) ||
+			enry.IsConfiguration(f.Name()) ||
+			(!isFalse(isDocumentation) && enry.IsDocumentation(f.Name())) {
+			continue
+		}
+
+		// If content can not be read or file is too big just do detection by filename
+
+		if f.Size() <= bigFileSize {
+			if err := writeID(f.ID.String()); err != nil {
+				return nil, err
+			}
+			_, _, size, err := ReadBatchLine(batchReader)
+			if err != nil {
+				log.Debug("Error reading blob: %s Err: %v", f.ID.String(), err)
+				return nil, err
+			}
+
+			sizeToRead := size
+			discard := int64(1)
+			if size > fileSizeLimit {
+				sizeToRead = fileSizeLimit
+				discard = size - fileSizeLimit + 1
+			}
+
+			_, err = contentBuf.ReadFrom(io.LimitReader(batchReader, sizeToRead))
+			if err != nil {
+				return nil, err
+			}
+			content = contentBuf.Bytes()
+			if err := DiscardFull(batchReader, discard); err != nil {
+				return nil, err
+			}
+		}
+		if !isTrue(isGenerated) && enry.IsGenerated(f.Name(), content) {
+			continue
+		}
+
+		// FIXME: Why can't we split this and the IsGenerated tests to avoid reading the blob unless absolutely necessary?
+		// - eg. do the all the detection tests using filename first before reading content.
+		language := analyze.GetCodeLanguage(f.Name(), content)
+		if language == "" {
+			continue
+		}
+
+		// group languages, such as Pug -> HTML; SCSS -> CSS
+		group := enry.GetLanguageGroup(language)
+		if group != "" {
+			language = group
+		}
+
+		included, checked := includedLanguage[language]
+		langType := enry.GetLanguageType(language)
+		if !checked {
+			included = langType == enry.Programming || langType == enry.Markup
+			if !included && (isTrue(isDetectable) || (langType == enry.Prose && isFalse(isDocumentation))) {
+				included = true
+			}
+			includedLanguage[language] = included
+		}
+		if included {
+			sizes[language] += f.Size()
+		} else if len(sizes) == 0 && (firstExcludedLanguage == "" || firstExcludedLanguage == language) {
+			// Only consider Programming or Markup languages as fallback
+			if !(langType == enry.Programming || langType == enry.Markup) {
+				continue
+			}
+			firstExcludedLanguage = language
+			firstExcludedLanguageSize += f.Size()
+		}
+	}
+
+	// If there are no included languages add the first excluded language
+	if len(sizes) == 0 && firstExcludedLanguage != "" {
+		sizes[firstExcludedLanguage] = firstExcludedLanguageSize
+	}
+
+	return mergeLanguageStats(sizes), nil
+}