Add support for sha256 repositories (#23894)

Currently only SHA1 repositories are supported by Gitea. This adds
support for alternate SHA256 with the additional aim of easier support
for additional hash types in the future.

Fixes: #13794
Limited by: https://github.com/go-git/go-git/issues/899
Depend on: #28138

<img width="776" alt="图片" src="5448c9a7-608e-4341-a149-5dd0069c9447">

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>

models/migrations/v1_22/v286.go

@@ -0,0 +1,104 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+package v1_22 //nolint
+
+import (
+	"errors"
+	"fmt"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"xorm.io/xorm"
+)
+
+func expandHashReferencesToSha256(x *xorm.Engine) error {
+	alteredTables := [][2]string{
+		{"commit_status", "context_hash"},
+		{"comment", "commit_sha"},
+		{"pull_request", "merge_base"},
+		{"pull_request", "merged_commit_id"},
+		{"review", "commit_id"},
+		{"review_state", "commit_sha"},
+		{"repo_archiver", "commit_id"},
+		{"release", "sha1"},
+		{"repo_indexer_status", "commit_sha"},
+	}
+
+	db := x.NewSession()
+	defer db.Close()
+
+	if err := db.Begin(); err != nil {
+		return err
+	}
+
+	if !setting.Database.Type.IsSQLite3() {
+		if setting.Database.Type.IsMSSQL() {
+			// drop indexes that need to be re-created afterwards
+			droppedIndexes := []string{
+				"DROP INDEX commit_status.IDX_commit_status_context_hash",
+				"DROP INDEX review_state.UQE_review_state_pull_commit_user",
+				"DROP INDEX repo_archiver.UQE_repo_archiver_s",
+			}
+			for _, s := range droppedIndexes {
+				_, err := db.Exec(s)
+				if err != nil {
+					return errors.New(s + " " + err.Error())
+				}
+			}
+		}
+
+		for _, alts := range alteredTables {
+			var err error
+			if setting.Database.Type.IsMySQL() {
+				_, err = db.Exec(fmt.Sprintf("ALTER TABLE `%s` MODIFY COLUMN `%s` VARCHAR(64)", alts[0], alts[1]))
+			} else if setting.Database.Type.IsMSSQL() {
+				_, err = db.Exec(fmt.Sprintf("ALTER TABLE `%s` ALTER COLUMN `%s` VARCHAR(64)", alts[0], alts[1]))
+			} else {
+				_, err = db.Exec(fmt.Sprintf("ALTER TABLE `%s` ALTER COLUMN `%s` TYPE VARCHAR(64)", alts[0], alts[1]))
+			}
+			if err != nil {
+				return fmt.Errorf("alter column '%s' of table '%s' failed: %w", alts[1], alts[0], err)
+			}
+		}
+
+		if setting.Database.Type.IsMSSQL() {
+			recreateIndexes := []string{
+				"CREATE INDEX IDX_commit_status_context_hash ON commit_status(context_hash)",
+				"CREATE UNIQUE INDEX UQE_review_state_pull_commit_user ON review_state(user_id, pull_id, commit_sha)",
+				"CREATE UNIQUE INDEX UQE_repo_archiver_s ON repo_archiver(repo_id, type, commit_id)",
+			}
+			for _, s := range recreateIndexes {
+				_, err := db.Exec(s)
+				if err != nil {
+					return errors.New(s + " " + err.Error())
+				}
+			}
+		}
+	}
+	log.Debug("Updated database tables to hold SHA256 git hash references")
+
+	return db.Commit()
+}
+
+func addObjectFormatNameToRepository(x *xorm.Engine) error {
+	type Repository struct {
+		ObjectFormatName string `xorm:"VARCHAR(6) NOT NULL DEFAULT 'sha1'"`
+	}
+
+	if err := x.Sync(new(Repository)); err != nil {
+		return err
+	}
+
+	// Here to catch weird edge-cases where column constraints above are
+	// not applied by the DB backend
+	_, err := x.Exec("UPDATE repository set object_format_name = 'sha1' WHERE object_format_name = '' or object_format_name IS NULL")
+	return err
+}
+
+func AdjustDBForSha256(x *xorm.Engine) error {
+	if err := expandHashReferencesToSha256(x); err != nil {
+		return err
+	}
+	return addObjectFormatNameToRepository(x)
+}