add submodule diff links

This adds links to submodules in diffs, similar to the existing link
when viewing a repo at a specific commit. It does this by expanding
diff parsing to recognize changes to submodules, and find the specific
refs that are added, deleted or changed.

The templates are updated to add either a link to the submodule at a
commit, or the diff between two commits in the event that the
submodule is updated.

A slight refactor was done to simplify calling RefURL on the
submodule.

Author: bohde

modules/git/commit_submodule_file.go

@@ -11,6 +11,8 @@ import (
 	"path"
 	"regexp"
 	"strings"
+
+	"code.gitea.io/gitea/modules/setting"
 )
 
 var scpSyntax = regexp.MustCompile(`^([a-zA-Z0-9_]+@)?([a-zA-Z0-9._-]+):(.*)$`)
@@ -101,8 +103,8 @@ func getRefURL(refURL, urlPrefix, repoFullName, sshDomain string) string {
 
 // RefURL guesses and returns reference URL.
 // FIXME: template passes AppURL as urlPrefix, it needs to figure out the correct approach (no hard-coded AppURL anymore)
-func (sf *CommitSubModuleFile) RefURL(urlPrefix, repoFullName, sshDomain string) string {
-	return getRefURL(sf.refURL, urlPrefix, repoFullName, sshDomain)
+func (sf *CommitSubModuleFile) RefURL(repoFullName string) string {
+	return getRefURL(sf.refURL, setting.AppURL, repoFullName, setting.SSH.Domain)
 }
 
 // RefID returns reference ID.

options/locale/locale_en-US.ini

@@ -2627,6 +2627,11 @@ diff.image.overlay = Overlay
 diff.has_escaped = This line has hidden Unicode characters
 diff.show_file_tree = Show file tree
 diff.hide_file_tree = Hide file tree
+diff.submodule_added = Submodule %s added at %s
+diff.submodule_added_link = Submodule <a href="%[1]s">%[2]s</a> added at <a href="%[1]s/commit/%[4]s">%[3]s</a>
+diff.submodule_deleted = Submodule %s deleted from %s
+diff.submodule_updated = Submodule %s updated from %s to %s
+diff.submodule_updated_link = Submodule <a href="%[1]s">%[2]s</a> updated <a href="%[1]s/compare/%[4]s...%[6]s">from %[3]s to %[5]s</a>
 
 releases.desc = Track project versions and downloads.
 release.releases = Releases

routers/web/repo/view.go

@@ -309,7 +309,6 @@ func renderDirectoryFiles(ctx *context.Context, timeout time.Duration) git.Entri
 	}
 
 	ctx.Data["TreeLink"] = treeLink
-	ctx.Data["SSHDomain"] = setting.SSH.Domain
 
 	return allEntries
 }

services/gitdiff/gitdiff.go

@@ -372,6 +372,7 @@ type DiffFile struct {
 	Language                  string
 	Mode                      string
 	OldMode                   string
+	SubmoduleInfo             *SubmoduleInfo
 }
 
 // GetType returns type of diff file.
@@ -915,6 +916,17 @@ func parseHunks(ctx context.Context, curFile *DiffFile, maxLines, maxLineCharact
 				}
 			}
 			curSection.Lines = append(curSection.Lines, diffLine)
+
+			// Parse submodule additions
+			if curFile.IsSubmodule {
+				if curFile.SubmoduleInfo == nil {
+					curFile.SubmoduleInfo = &SubmoduleInfo{}
+				}
+
+				if ref, found := bytes.CutPrefix(lineBytes, []byte("+Subproject commit ")); found {
+					curFile.SubmoduleInfo.NewRefID = string(bytes.TrimSpace(ref))
+				}
+			}
 		case '-':
 			curFileLinesCount++
 			curFile.Deletion++
@@ -936,6 +948,17 @@ func parseHunks(ctx context.Context, curFile *DiffFile, maxLines, maxLineCharact
 				lastLeftIdx = len(curSection.Lines)
 			}
 			curSection.Lines = append(curSection.Lines, diffLine)
+
+			// Parse submodule deletion
+			if curFile.IsSubmodule {
+				if curFile.SubmoduleInfo == nil {
+					curFile.SubmoduleInfo = &SubmoduleInfo{}
+				}
+
+				if ref, found := bytes.CutPrefix(lineBytes, []byte("-Subproject commit ")); found {
+					curFile.SubmoduleInfo.PreviousRefID = string(bytes.TrimSpace(ref))
+				}
+			}
 		case ' ':
 			curFileLinesCount++
 			if maxLines > -1 && curFileLinesCount >= maxLines {
@@ -1195,6 +1218,14 @@ func GetDiff(ctx context.Context, gitRepo *git.Repository, opts *DiffOptions, fi
 			}
 		}
 
+		// Populate Submodule URLs
+		if diffFile.IsSubmodule && diffFile.SubmoduleInfo != nil {
+			err := diffFile.SubmoduleInfo.PopulateURL(diffFile, beforeCommit, commit)
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		if !isVendored.Has() {
 			isVendored = optional.Some(analyze.IsVendor(diffFile.Name))
 		}

services/gitdiff/submodule.go

@@ -0,0 +1,55 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitdiff
+
+import "code.gitea.io/gitea/modules/git"
+
+type SubmoduleInfo struct {
+	SubmoduleURL  string
+	NewRefID      string
+	PreviousRefID string
+}
+
+func (si *SubmoduleInfo) PopulateURL(diffFile *DiffFile, leftCommit, rightCommit *git.Commit) error {
+	// If the submodule is removed, we need to check it at the left commit
+	if diffFile.IsDeleted {
+		if leftCommit == nil {
+			return nil
+		}
+
+		submodule, err := leftCommit.GetSubModule(diffFile.GetDiffFileName())
+		if err != nil {
+			return err
+		}
+
+		if submodule != nil {
+			si.SubmoduleURL = submodule.URL
+		}
+
+		return nil
+	}
+
+	// Even if the submodule path is updated, we check this at the right commit
+	submodule, err := rightCommit.GetSubModule(diffFile.Name)
+	if err != nil {
+		return err
+	}
+
+	if submodule != nil {
+		si.SubmoduleURL = submodule.URL
+	}
+	return nil
+}
+
+func (si *SubmoduleInfo) RefID() string {
+	if si.NewRefID != "" {
+		return si.NewRefID
+	}
+	return si.PreviousRefID
+}
+
+// RefURL guesses and returns reference URL.
+func (si *SubmoduleInfo) RefURL(repoFullName string) string {
+	return git.NewCommitSubModuleFile(si.SubmoduleURL, si.RefID()).RefURL(repoFullName)
+}

services/gitdiff/submodule_test.go

@@ -0,0 +1,217 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitdiff
+
+import (
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseSubmoduleInfo(t *testing.T) {
+	type testcase struct {
+		name    string
+		gitdiff string
+		infos   map[int]SubmoduleInfo
+	}
+
+	tests := []testcase{
+		{
+			name: "added",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+new file mode 100644
+index 0000000..4ac13c1
+--- /dev/null
++++ b/.gitmodules
+@@ -0,0 +1,3 @@
++[submodule "gitea-mirror"]
++	path = gitea-mirror
++	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea-mirror b/gitea-mirror
+new file mode 160000
+index 0000000..68972a9
+--- /dev/null
++++ b/gitea-mirror
+@@ -0,0 +1 @@
++Subproject commit 68972a994719ae5c74e28d8fa82fa27c23399bc8
+`,
+			infos: map[int]SubmoduleInfo{
+				1: {NewRefID: "68972a994719ae5c74e28d8fa82fa27c23399bc8"},
+			},
+		},
+		{
+			name: "updated",
+			gitdiff: `diff --git a/gitea-mirror b/gitea-mirror
+index 68972a9..c8ffe77 160000
+--- a/gitea-mirror
++++ b/gitea-mirror
+@@ -1 +1 @@
+-Subproject commit 68972a994719ae5c74e28d8fa82fa27c23399bc8
++Subproject commit c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d
+`,
+			infos: map[int]SubmoduleInfo{
+				0: {
+					PreviousRefID: "68972a994719ae5c74e28d8fa82fa27c23399bc8",
+					NewRefID:      "c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d",
+				},
+			},
+		},
+		{
+			name: "rename",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+index 4ac13c1..0510edd 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -1,3 +1,3 @@
+ [submodule "gitea-mirror"]
+-	path = gitea-mirror
++	path = gitea
+ 	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea-mirror b/gitea
+similarity index 100%
+rename from gitea-mirror
+rename to gitea
+`,
+		},
+		{
+			name: "deleted",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+index 0510edd..e69de29 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -1,3 +0,0 @@
+-[submodule "gitea-mirror"]
+-	path = gitea
+-	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea b/gitea
+deleted file mode 160000
+index c8ffe77..0000000
+--- a/gitea
++++ /dev/null
+@@ -1 +0,0 @@
+-Subproject commit c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d
+`,
+			infos: map[int]SubmoduleInfo{
+				1: {
+					PreviousRefID: "c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d",
+				},
+			},
+		},
+		{
+			name: "moved and updated",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+index 0510edd..bced3d8 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -1,3 +1,3 @@
+ [submodule "gitea-mirror"]
+-	path = gitea
++	path = gitea-1.22
+ 	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea b/gitea
+deleted file mode 160000
+index c8ffe77..0000000
+--- a/gitea
++++ /dev/null
+@@ -1 +0,0 @@
+-Subproject commit c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d
+diff --git a/gitea-1.22 b/gitea-1.22
+new file mode 160000
+index 0000000..8eefa1f
+--- /dev/null
++++ b/gitea-1.22
+@@ -0,0 +1 @@
++Subproject commit 8eefa1f6dedf2488db2c9e12c916e8e51f673160
+`,
+			infos: map[int]SubmoduleInfo{
+				1: {
+					PreviousRefID: "c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d",
+				},
+				2: {
+					NewRefID: "8eefa1f6dedf2488db2c9e12c916e8e51f673160",
+				},
+			},
+		},
+		{
+			name: "converted to file",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+index 0510edd..e69de29 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -1,3 +0,0 @@
+-[submodule "gitea-mirror"]
+-	path = gitea
+-	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea b/gitea
+deleted file mode 160000
+index c8ffe77..0000000
+--- a/gitea
++++ /dev/null
+@@ -1 +0,0 @@
+-Subproject commit c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d
+diff --git a/gitea b/gitea
+new file mode 100644
+index 0000000..33a9488
+--- /dev/null
++++ b/gitea
+@@ -0,0 +1 @@
++example
+`,
+			infos: map[int]SubmoduleInfo{
+				1: {
+					PreviousRefID: "c8ffe777cf9c5bb47a38e3e0b3a3b5de6cd8813d",
+				},
+			},
+		},
+		{
+			name: "converted to submodule",
+			gitdiff: `diff --git a/.gitmodules b/.gitmodules
+index e69de29..14ee267 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -0,0 +1,3 @@
++[submodule "gitea"]
++	path = gitea
++	url = https://gitea.com/gitea/gitea-mirror
+diff --git a/gitea b/gitea
+deleted file mode 100644
+index 33a9488..0000000
+--- a/gitea
++++ /dev/null
+@@ -1 +0,0 @@
+-example
+diff --git a/gitea b/gitea
+new file mode 160000
+index 0000000..68972a9
+--- /dev/null
++++ b/gitea
+@@ -0,0 +1 @@
++Subproject commit 68972a994719ae5c74e28d8fa82fa27c23399bc8
+`,
+			infos: map[int]SubmoduleInfo{
+				2: {
+					NewRefID: "68972a994719ae5c74e28d8fa82fa27c23399bc8",
+				},
+			},
+		},
+	}
+
+	for _, testcase := range tests {
+		testcase := testcase
+		t.Run(testcase.name, func(t *testing.T) {
+			diff, err := ParsePatch(db.DefaultContext, setting.Git.MaxGitDiffLines, setting.Git.MaxGitDiffLineCharacters, setting.Git.MaxGitDiffFiles, strings.NewReader(testcase.gitdiff), "")
+			assert.NoError(t, err)
+
+			for i, expected := range testcase.infos {
+				actual := diff.Files[i]
+				assert.NotNil(t, actual)
+				assert.Equal(t, expected, *actual.SubmoduleInfo)
+			}
+		})
+	}
+}