Let gitea_commit take a large patch from a hash-checked spool file (issue 852)

A feature's diff is megabytes, too large to type into a call. gitea_commit now also takes patch_file, the
random hex name of a file in the module's spool directory /var/lib/mesh/forge-patches (mode 0733, owned by
the machine's account), with patch_sha256. The tool reads only that directory, never through a symlink or a
hard link, refuses a file whose SHA-256 differs, applies it as it applies patch, and removes it.

Co-Authored-By: Claude <noreply@anthropic.com>

modules/gitea/cmd/forge/commit.go

@@ -35,6 +35,11 @@ type CommitAsk struct {
 	Message     string
 	Files       []FileChange
 	Patch       string // a unified diff, as git diff writes it, instead of Files
+	// PatchFile is the name of a file in the spool directory holding the patch (novox/hq issue 852), with the
+	// SHA-256 its caller says it has; commitAsk reads it into Patch.
+	PatchFile      string
+	PatchSHA256    string
+	patchFileGiven bool
 }
 
 // Committed is what gitea_commit made.
@@ -69,6 +74,11 @@ func readCommitAsk(args map[string]any) (CommitAsk, error) {
 	a := CommitAsk{Owner: text(args, "owner"), Repo: text(args, "repo"), Branch: text(args, "branch"),
 		Base: text(args, "base"), Message: strings.TrimSpace(raw(args, "message"))}
 	a.Patch = raw(args, "patch")
+	if v, ok := args["patch_file"]; ok && v != nil {
+		a.patchFileGiven = true
+		a.PatchFile = raw(args, "patch_file")
+	}
+	a.PatchSHA256 = strings.ToLower(strings.TrimSpace(raw(args, "patch_sha256")))
 	if a.Branch == "" {
 		return a, refuse("branch is required: the branch the commit goes on, a branch of its own (created from base when absent). Nothing was sent")
 	}
@@ -111,11 +121,23 @@ func readCommitAsk(args map[string]any) (CommitAsk, error) {
 			a.Files = append(a.Files, fc)
 		}
 	}
+	sources := 0
+	for _, g := range []bool{len(a.Files) > 0, strings.TrimSpace(a.Patch) != "", a.patchFileGiven} {
+		if g {
+			sources++
+		}
+	}
 	switch {
-	case len(a.Files) == 0 && strings.TrimSpace(a.Patch) == "":
-		return a, refuse("give files (each {path, content | content_base64 | delete: true}) or patch (a unified diff, as git diff writes it). Nothing was sent")
-	case len(a.Files) > 0 && strings.TrimSpace(a.Patch) != "":
-		return a, refuse("give files or patch, not both: one commit carries one of them. Nothing was sent")
+	case sources == 0:
+		return a, refuse("give files (each {path, content | content_base64 | delete: true}), patch (a unified diff, as git diff writes it) or patch_file (the name of a patch in the spool directory). Nothing was sent")
+	case sources > 1:
+		return a, refuse("give files, patch or patch_file, not more than one: one commit carries one of them. Nothing was sent")
+	case a.PatchSHA256 != "" && !a.patchFileGiven:
+		return a, refuse("patch_sha256 goes with patch_file only. Nothing was sent")
+	case a.patchFileGiven:
+		if err := checkPatchFileAsk(a); err != nil {
+			return a, err
+		}
 	case len(a.Files) > maxFiles:
 		return a, refuse("%d files is more than the %d one commit carries. Nothing was sent", len(a.Files), maxFiles)
 	case len(a.Patch) > maxPatchBytes:
@@ -134,13 +156,13 @@ func readCommitAsk(args map[string]any) (CommitAsk, error) {
 			return a, refuse("%s is named twice in files. Nothing was sent", fc.Path)
 		}
 		seen[fc.Path] = true
-		given := 0
+		have := 0
 		for _, g := range []bool{fc.Content != nil, fc.ContentBase64 != nil, fc.Delete} {
 			if g {
-				given++
+				have++
 			}
 		}
-		if given != 1 {
+		if have != 1 {
 			return a, refuse("files[%d] (%s) needs exactly one of content, content_base64 or delete: true. Nothing was sent", i, fc.Path)
 		}
 		if fc.Content != nil && !utf8.ValidString(*fc.Content) {