feat: Add support for dynamic matrix evaluation in Gitea Actions workflows (#36564)

Adds dynamic matrix evaluation to Gitea Actions: a job's
`strategy.matrix` can be built from the outputs of the jobs it needs.

```yaml
jobs:
  generate:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set.outputs.result }}
    steps:
      - id: set
        run: echo "result=[1,2,3]" >> $GITHUB_OUTPUT

  build:
    needs: [generate]
    runs-on: ubuntu-latest
    strategy:
      matrix:
        version: ${{ fromJson(needs.generate.outputs.matrix) }}
    steps:
      - run: echo "building ${{ matrix.version }}"
```

Such a matrix cannot be expanded at planning time, so the job is planned
as a single placeholder and expanded by the job emitter once its needs
finish. Each combination is then gated by `if:` and concurrency as
usual.

- A matrix that resolves to no combination fails the job, as on GitHub.
- Expansion is capped at `MaxJobNumPerRun`.
- Workflows without a needs-dependent matrix are unaffected.

Fixes https://github.com/go-gitea/gitea/issues/25179

---------

Signed-off-by: Pascal Zimmermann <pascal.zimmermann@theiotstudio.com>
Signed-off-by: ZPascal <pascal.zimmermann@theiotstudio.com>
Co-authored-by: Claude <claude-sonnet-4-5@anthropic.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.8) <noreply@anthropic.com>
Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>

modelmigration/migrations.go

@@ -424,6 +424,7 @@ func prepareMigrationTasks() []*migration {
 		// Gitea 1.27.0 ends at migration ID number 342 (database version 343)
 
 		newMigration(343, "Add max_parallel column to action_run_job", v1_28.AddMaxParallelToActionRunJob),
+		newMigration(344, "Add deferred-matrix columns to ActionRunJob", v1_28.AddDeferredMatrixColumnsToActionRunJob),
 	}
 	return preparedMigrations
 }

modelmigration/v1_28/v344.go

@@ -0,0 +1,25 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_28
+
+import (
+	"gitea.dev/modelmigration/base"
+
+	"xorm.io/xorm"
+)
+
+// AddDeferredMatrixColumnsToActionRunJob adds the columns backing deferred (dynamic) matrix expansion
+func AddDeferredMatrixColumnsToActionRunJob(x base.EngineMigration) error {
+	type ActionRunJob struct {
+		// IsMatrixDeferred marks jobs whose matrix depends on other jobs' outputs and is therefore expanded only once those jobs finish;
+		IsMatrixDeferred bool `xorm:"NOT NULL DEFAULT FALSE"`
+		// DeferredMatrixPayload preserves the raw, unevaluated payload across expansion so a rerun can re-derive the matrix
+		DeferredMatrixPayload []byte `xorm:"LONGBLOB"`
+	}
+	_, err := x.SyncWithOptions(xorm.SyncOptions{
+		IgnoreDropIndices: true,
+		IgnoreConstrains:  true,
+	}, new(ActionRunJob))
+	return err
+}