Pr head checkout fallback (#231)

* Add commit checkout fallback to PR head branch checkout method

* Validate commit checkout fallback required params

* Add some logs to commit checkout fallback

* Mock pr head branch checkout error

* Fix commit checkout error mocking

* Remove commit checkout error mocking

* Add fork repo PR handling to the commit checkout fallback

* Remove error mock

Author: godrei

gitclone/checkout.go

@@ -314,6 +314,33 @@ func createCheckoutStrategy(checkoutMethod CheckoutMethod, cfg Config, patchFile
 
 			return checkoutCommit{
 				params: *params,
+				fallbackCheckout: func(gitCmd git.Git) error {
+					log.Warnf("Using commit checkout strategy with PR source branch")
+
+					if cfg.Branch == "" || cfg.Commit == "" {
+						return fmt.Errorf("inconsistent checkout strategy and checkout params: branch=%s, commit=%s", cfg.Branch, cfg.Commit)
+					}
+
+					branchRef := refsHeadsPrefix + cfg.Branch
+					commitCheckoutFallbackFetchOpts := selectFetchOptions(CheckoutCommitMethod, cfg.CloneDepth, cfg.FetchTags, cfg.UpdateSubmodules, len(cfg.SparseDirectories) != 0)
+					commitCheckoutFallbackFallback := selectFallbacks(CheckoutCommitMethod, commitCheckoutFallbackFetchOpts)
+
+					prRepositoryURL := ""
+					if isFork(cfg.RepositoryURL, cfg.PRSourceRepositoryURL) {
+						prRepositoryURL = cfg.PRSourceRepositoryURL
+					}
+
+					params, err := NewCommitParams(cfg.Commit, branchRef, prRepositoryURL)
+					if err != nil {
+						return err
+					}
+
+					commitCheckoutFallbackCheckoutMethod := checkoutCommit{
+						params: *params,
+					}
+
+					return commitCheckoutFallbackCheckoutMethod.do(gitCmd, commitCheckoutFallbackFetchOpts, commitCheckoutFallbackFallback)
+				},
 			}, nil
 		}
 	case CheckoutForkCommitMethod:

gitclone/checkout_method_pr_auto_merge_branch.go

@@ -3,7 +3,7 @@ package gitclone
 import (
 	"fmt"
 	"strings"
-
+	
 	"github.com/bitrise-io/go-utils/command/git"
 	"github.com/bitrise-io/go-utils/log"
 )
@@ -42,9 +42,8 @@ type fallbackCheckoutFunc func(gitCmd git.Git) error
 
 func (c checkoutPRMergeRef) do(gitCmd git.Git, fetchOpts fetchOptions, fallback fallbackRetry) error {
 	if err := c.performCheckout(gitCmd, fetchOpts, fallback); err != nil {
-		log.Warnf("Failed to checkout PR merge branch: %s", err)
-
 		if c.fallbackCheckout != nil {
+			log.Warnf("Failed to checkout PR merge branch: %s", err)
 			return c.fallbackCheckout(gitCmd)
 		}
 		return err

gitclone/checkout_method_simple.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 
 	"github.com/bitrise-io/go-utils/command/git"
+	"github.com/bitrise-io/go-utils/log"
 )
 
 // checkoutNone
@@ -40,10 +41,22 @@ func NewCommitParams(commit, branchRef, sourceRepoURL string) (*CommitParams, er
 
 // checkoutCommit
 type checkoutCommit struct {
-	params CommitParams
+	params           CommitParams
+	fallbackCheckout fallbackCheckoutFunc
 }
 
 func (c checkoutCommit) do(gitCmd git.Git, fetchOptions fetchOptions, fallback fallbackRetry) error {
+	if err := c.performCheckout(gitCmd, fetchOptions, fallback); err != nil {
+		if c.fallbackCheckout != nil {
+			log.Warnf("Failed to checkout commit: %s", err)
+			return c.fallbackCheckout(gitCmd)
+		}
+		return err
+	}
+	return nil
+}
+
+func (c checkoutCommit) performCheckout(gitCmd git.Git, fetchOptions fetchOptions, fallback fallbackRetry) error {
 	remote := originRemoteName
 	if c.params.SourceRepoURL != "" {
 		remote = forkRemoteName