[API] Get a single commit via Ref (#10915)

* GET /repos/:owner/:repo/commits/:ref

* add Validation Checks

* Fix & Extend TEST

* add two new tast cases

3 files changed, 29 insertions, 16 deletions

diff --git a/modules/convert/convert.go b/modules/convert/convert.go
index e11a599fd6..30d240f809 100644
--- a/modules/convert/convert.go
+++ b/modules/convert/convert.go
@@ -386,7 +386,6 @@ func ToCommitUser(sig *git.Signature) *api.CommitUser {
 func ToCommitMeta(repo *models.Repository, tag *git.Tag) *api.CommitMeta {
 	return &api.CommitMeta{
 		SHA: tag.Object.String(),
-		// TODO: Add the /commits API endpoint and use it here (https://developer.github.com/v3/repos/commits/#get-a-single-commit)
 		URL: util.URLJoin(repo.APIURL(), "git/commits", tag.ID.String()),
 	}
 }
diff --git a/modules/git/sha1.go b/modules/git/sha1.go
index 59b8335736..bccc94f103 100644
--- a/modules/git/sha1.go
+++ b/modules/git/sha1.go
@@ -8,6 +8,7 @@ package git
 import (
 	"encoding/hex"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -16,6 +17,9 @@ import (
 // EmptySHA defines empty git SHA
 const EmptySHA = "0000000000000000000000000000000000000000"
 
+// SHAPattern can be used to determine if a string is an valid sha
+var SHAPattern = regexp.MustCompile(`^[0-9a-f]{4,40}$`)
+
 // SHA1 a git commit name
 type SHA1 = plumbing.Hash
 
diff --git a/modules/validation/binding.go b/modules/validation/binding.go
index 6ed75b50fb..1c67878ea1 100644
--- a/modules/validation/binding.go
+++ b/modules/validation/binding.go
@@ -22,12 +22,32 @@ const (
 )
 
 var (
-	// GitRefNamePattern is regular expression with unallowed characters in git reference name
+	// GitRefNamePatternInvalid is regular expression with unallowed characters in git reference name
 	// They cannot have ASCII control characters (i.e. bytes whose values are lower than \040, or \177 DEL), space, tilde ~, caret ^, or colon : anywhere.
 	// They cannot have question-mark ?, asterisk *, or open bracket [ anywhere
-	GitRefNamePattern = regexp.MustCompile(`[\000-\037\177 \\~^:?*[]+`)
+	GitRefNamePatternInvalid = regexp.MustCompile(`[\000-\037\177 \\~^:?*[]+`)
 )
 
+// CheckGitRefAdditionalRulesValid check name is valid on additional rules
+func CheckGitRefAdditionalRulesValid(name string) bool {
+
+	// Additional rules as described at https://www.kernel.org/pub/software/scm/git/docs/git-check-ref-format.html
+	if strings.HasPrefix(name, "/") || strings.HasSuffix(name, "/") ||
+		strings.HasSuffix(name, ".") || strings.Contains(name, "..") ||
+		strings.Contains(name, "//") || strings.Contains(name, "@{") ||
+		name == "@" {
+		return false
+	}
+	parts := strings.Split(name, "/")
+	for _, part := range parts {
+		if strings.HasSuffix(part, ".lock") || strings.HasPrefix(part, ".") {
+			return false
+		}
+	}
+
+	return true
+}
+
 // AddBindingRules adds additional binding rules
 func AddBindingRules() {
 	addGitRefNameBindingRule()
@@ -44,25 +64,15 @@ func addGitRefNameBindingRule() {
 		IsValid: func(errs binding.Errors, name string, val interface{}) (bool, binding.Errors) {
 			str := fmt.Sprintf("%v", val)
 
-			if GitRefNamePattern.MatchString(str) {
+			if GitRefNamePatternInvalid.MatchString(str) {
 				errs.Add([]string{name}, ErrGitRefName, "GitRefName")
 				return false, errs
 			}
-			// Additional rules as described at https://www.kernel.org/pub/software/scm/git/docs/git-check-ref-format.html
-			if strings.HasPrefix(str, "/") || strings.HasSuffix(str, "/") ||
-				strings.HasSuffix(str, ".") || strings.Contains(str, "..") ||
-				strings.Contains(str, "//") || strings.Contains(str, "@{") ||
-				str == "@" {
+
+			if !CheckGitRefAdditionalRulesValid(str) {
 				errs.Add([]string{name}, ErrGitRefName, "GitRefName")
 				return false, errs
 			}
-			parts := strings.Split(str, "/")
-			for _, part := range parts {
-				if strings.HasSuffix(part, ".lock") || strings.HasPrefix(part, ".") {
-					errs.Add([]string{name}, ErrGitRefName, "GitRefName")
-					return false, errs
-				}
-			}
 
 			return true, errs
 		},