Adjust error reporting from merge failures and use LC_ALL=C for git (#8548)

There are two major components to this PR:

* This PR handles merge and rebase failures from merging a little more nicely with Flash errors rather a 500.
* All git commands are run in the LC_ALL="C" environment to ensure that error messages are in English. This DefaultLocale is defined in a way that if necessary (due to platform weirdness) it can be overridden at build time using LDFLAGS="-X "code.gitea.io/gitea/modules/git.DefaultLocale=C"" with C changed for the locale as necessary.

1 files changed, 137 insertions, 0 deletions

diff --git a/integrations/pull_merge_test.go b/integrations/pull_merge_test.go
index 27f9fc6bb9..a63e27e149 100644
--- a/integrations/pull_merge_test.go
+++ b/integrations/pull_merge_test.go
@@ -5,15 +5,22 @@
 package integrations
 
 import (
+	"bytes"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"path"
 	"strings"
 	"testing"
+	"time"
 
 	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/git"
+	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/test"
+	"code.gitea.io/gitea/services/pull"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/unknwon/i18n"
@@ -202,3 +209,133 @@ func TestCantMergeWorkInProgress(t *testing.T) {
 		assert.Equal(t, replacer.Replace(expected), text, "Unable to find WIP text")
 	})
 }
+
+func TestCantMergeConflict(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, giteaURL *url.URL) {
+		prepareTestEnv(t)
+		session := loginUser(t, "user1")
+		testRepoFork(t, session, "user2", "repo1", "user1", "repo1")
+		testEditFileToNewBranch(t, session, "user1", "repo1", "master", "conflict", "README.md", "Hello, World (Edited Once)\n")
+		testEditFileToNewBranch(t, session, "user1", "repo1", "master", "base", "README.md", "Hello, World (Edited Twice)\n")
+
+		// Use API to create a conflicting pr
+		token := getTokenForLoggedInUser(t, session)
+		req := NewRequestWithJSON(t, http.MethodPost, fmt.Sprintf("/api/v1/repos/%s/%s/pulls?token=%s", "user1", "repo1", token), &api.CreatePullRequestOption{
+			Head:  "conflict",
+			Base:  "base",
+			Title: "create a conflicting pr",
+		})
+		session.MakeRequest(t, req, 201)
+
+		// Now this PR will be marked conflict - or at least a race will do - so drop down to pure code at this point...
+		user1 := models.AssertExistsAndLoadBean(t, &models.User{
+			Name: "user1",
+		}).(*models.User)
+		repo1 := models.AssertExistsAndLoadBean(t, &models.Repository{
+			OwnerID: user1.ID,
+			Name:    "repo1",
+		}).(*models.Repository)
+
+		pr := models.AssertExistsAndLoadBean(t, &models.PullRequest{
+			HeadRepoID: repo1.ID,
+			BaseRepoID: repo1.ID,
+			HeadBranch: "conflict",
+			BaseBranch: "base",
+		}).(*models.PullRequest)
+
+		gitRepo, err := git.OpenRepository(models.RepoPath(user1.Name, repo1.Name))
+		assert.NoError(t, err)
+
+		err = pull.Merge(pr, user1, gitRepo, models.MergeStyleMerge, "CONFLICT")
+		assert.Error(t, err, "Merge should return an error due to conflict")
+		assert.True(t, models.IsErrMergeConflicts(err), "Merge error is not a conflict error")
+
+		err = pull.Merge(pr, user1, gitRepo, models.MergeStyleRebase, "CONFLICT")
+		assert.Error(t, err, "Merge should return an error due to conflict")
+		assert.True(t, models.IsErrRebaseConflicts(err), "Merge error is not a conflict error")
+	})
+}
+
+func TestCantMergeUnrelated(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, giteaURL *url.URL) {
+		prepareTestEnv(t)
+		session := loginUser(t, "user1")
+		testRepoFork(t, session, "user2", "repo1", "user1", "repo1")
+		testEditFileToNewBranch(t, session, "user1", "repo1", "master", "base", "README.md", "Hello, World (Edited Twice)\n")
+
+		// Now we want to create a commit on a branch that is totally unrelated to our current head
+		// Drop down to pure code at this point
+		user1 := models.AssertExistsAndLoadBean(t, &models.User{
+			Name: "user1",
+		}).(*models.User)
+		repo1 := models.AssertExistsAndLoadBean(t, &models.Repository{
+			OwnerID: user1.ID,
+			Name:    "repo1",
+		}).(*models.Repository)
+		path := models.RepoPath(user1.Name, repo1.Name)
+
+		_, err := git.NewCommand("read-tree", "--empty").RunInDir(path)
+		assert.NoError(t, err)
+
+		stdin := bytes.NewBufferString("Unrelated File")
+		var stdout strings.Builder
+		err = git.NewCommand("hash-object", "-w", "--stdin").RunInDirFullPipeline(path, &stdout, nil, stdin)
+		assert.NoError(t, err)
+		sha := strings.TrimSpace(stdout.String())
+
+		_, err = git.NewCommand("update-index", "--add", "--replace", "--cacheinfo", "100644", sha, "somewher-over-the-rainbow").RunInDir(path)
+		assert.NoError(t, err)
+
+		treeSha, err := git.NewCommand("write-tree").RunInDir(path)
+		assert.NoError(t, err)
+		treeSha = strings.TrimSpace(treeSha)
+
+		commitTimeStr := time.Now().Format(time.RFC3339)
+		doerSig := user1.NewGitSig()
+		env := append(os.Environ(),
+			"GIT_AUTHOR_NAME="+doerSig.Name,
+			"GIT_AUTHOR_EMAIL="+doerSig.Email,
+			"GIT_AUTHOR_DATE="+commitTimeStr,
+			"GIT_COMMITTER_NAME="+doerSig.Name,
+			"GIT_COMMITTER_EMAIL="+doerSig.Email,
+			"GIT_COMMITTER_DATE="+commitTimeStr,
+		)
+
+		messageBytes := new(bytes.Buffer)
+		_, _ = messageBytes.WriteString("Unrelated")
+		_, _ = messageBytes.WriteString("\n")
+
+		stdout.Reset()
+		err = git.NewCommand("commit-tree", treeSha).RunInDirTimeoutEnvFullPipeline(env, -1, path, &stdout, nil, messageBytes)
+		assert.NoError(t, err)
+		commitSha := strings.TrimSpace(stdout.String())
+
+		_, err = git.NewCommand("branch", "unrelated", commitSha).RunInDir(path)
+		assert.NoError(t, err)
+
+		testEditFileToNewBranch(t, session, "user1", "repo1", "master", "conflict", "README.md", "Hello, World (Edited Once)\n")
+
+		// Use API to create a conflicting pr
+		token := getTokenForLoggedInUser(t, session)
+		req := NewRequestWithJSON(t, http.MethodPost, fmt.Sprintf("/api/v1/repos/%s/%s/pulls?token=%s", "user1", "repo1", token), &api.CreatePullRequestOption{
+			Head:  "unrelated",
+			Base:  "base",
+			Title: "create an unrelated pr",
+		})
+		session.MakeRequest(t, req, 201)
+
+		// Now this PR could be marked conflict - or at least a race may occur - so drop down to pure code at this point...
+		gitRepo, err := git.OpenRepository(path)
+		assert.NoError(t, err)
+		pr := models.AssertExistsAndLoadBean(t, &models.PullRequest{
+			HeadRepoID: repo1.ID,
+			BaseRepoID: repo1.ID,
+			HeadBranch: "unrelated",
+			BaseBranch: "base",
+		}).(*models.PullRequest)
+
+		err = pull.Merge(pr, user1, gitRepo, models.MergeStyleMerge, "UNRELATED")
+		assert.Error(t, err, "Merge should return an error due to unrelated")
+		assert.True(t, models.IsErrMergeUnrelatedHistories(err), "Merge error is not a unrelated histories error")
+	})
+}