More efficiently parse shas for shaPostProcessor (#16101)

* More efficiently parse shas for shaPostProcessor

The shaPostProcessor currently repeatedly calls git rev-parse --verify on both backends
which is fine if there is only one thing that matches a sha - however if there are
multiple things then this becomes wildly inefficient.

This PR provides functions for both backends which are much faster to use.

Fix #16092

* Add ShaExistCache to RenderContext

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>

2 files changed, 42 insertions, 0 deletions

diff --git a/modules/git/repo_branch_gogit.go b/modules/git/repo_branch_gogit.go
index b00253f6ff..e8386b2dbd 100644
--- a/modules/git/repo_branch_gogit.go
+++ b/modules/git/repo_branch_gogit.go
@@ -13,6 +13,30 @@ import (
 	"github.com/go-git/go-git/v5/plumbing"
 )
 
+// IsObjectExist returns true if given reference exists in the repository.
+func (repo *Repository) IsObjectExist(name string) bool {
+	if name == "" {
+		return false
+	}
+
+	_, err := repo.gogitRepo.ResolveRevision(plumbing.Revision(name))
+
+	return err == nil
+}
+
+// IsReferenceExist returns true if given reference exists in the repository.
+func (repo *Repository) IsReferenceExist(name string) bool {
+	if name == "" {
+		return false
+	}
+
+	reference, err := repo.gogitRepo.Reference(plumbing.ReferenceName(name), true)
+	if err != nil {
+		return false
+	}
+	return reference.Type() != plumbing.InvalidReference
+}
+
 // IsBranchExist returns true if given branch exists in current repository.
 func (repo *Repository) IsBranchExist(name string) bool {
 	if name == "" {
diff --git a/modules/git/repo_branch_nogogit.go b/modules/git/repo_branch_nogogit.go
index 13ddcf06cf..dd34e48899 100644
--- a/modules/git/repo_branch_nogogit.go
+++ b/modules/git/repo_branch_nogogit.go
@@ -9,10 +9,28 @@ package git
 
 import (
 	"bufio"
+	"bytes"
 	"io"
 	"strings"
 )
 
+// IsObjectExist returns true if given reference exists in the repository.
+func (repo *Repository) IsObjectExist(name string) bool {
+	if name == "" {
+		return false
+	}
+
+	wr, rd, cancel := repo.CatFileBatchCheck()
+	defer cancel()
+	_, err := wr.Write([]byte(name + "\n"))
+	if err != nil {
+		log("Error writing to CatFileBatchCheck %v", err)
+		return false
+	}
+	sha, _, _, err := ReadBatchLine(rd)
+	return err == nil && bytes.HasPrefix(sha, []byte(strings.TrimSpace(name)))
+}
+
 // IsReferenceExist returns true if given reference exists in the repository.
 func (repo *Repository) IsReferenceExist(name string) bool {
 	if name == "" {