Propagate context and ensure git commands run in request context (#17868)

This PR continues the work in #17125 by progressively ensuring that git
commands run within the request context.

This now means that the if there is a git repo already open in the context it will be used instead of reopening it.

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/git/repo_base.go

@@ -0,0 +1,49 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+import (
+	"context"
+	"io"
+)
+
+// contextKey is a value for use with context.WithValue.
+type contextKey struct {
+	name string
+}
+
+// RepositoryContextKey is a context key. It is used with context.Value() to get the current Repository for the context
+var RepositoryContextKey = &contextKey{"repository"}
+
+// RepositoryFromContext attempts to get the repository from the context
+func RepositoryFromContext(ctx context.Context, path string) *Repository {
+	value := ctx.Value(RepositoryContextKey)
+	if value == nil {
+		return nil
+	}
+
+	if repo, ok := value.(*Repository); ok && repo != nil {
+		if repo.Path == path {
+			return repo
+		}
+	}
+
+	return nil
+}
+
+type nopCloser func()
+
+func (nopCloser) Close() error { return nil }
+
+// RepositoryFromContextOrOpen attempts to get the repository from the context or just opens it
+func RepositoryFromContextOrOpen(ctx context.Context, path string) (*Repository, io.Closer, error) {
+	gitRepo := RepositoryFromContext(ctx, path)
+	if gitRepo != nil {
+		return gitRepo, nopCloser(nil), nil
+	}
+
+	gitRepo, err := OpenRepositoryCtx(ctx, path)
+	return gitRepo, gitRepo, err
+}