Implement actions (#21937)

Close #13539.

Co-authored by: @lunny @appleboy @fuxiaohei and others.

Related projects:
- https://gitea.com/gitea/actions-proto-def
- https://gitea.com/gitea/actions-proto-go
- https://gitea.com/gitea/act
- https://gitea.com/gitea/act_runner

### Summary

The target of this PR is to bring a basic implementation of "Actions",
an internal CI/CD system of Gitea. That means even though it has been
merged, the state of the feature is **EXPERIMENTAL**, and please note
that:

- It is disabled by default;
- It shouldn't be used in a production environment currently;
- It shouldn't be used in a public Gitea instance currently;
- Breaking changes may be made before it's stable.

**Please comment on #13539 if you have any different product design
ideas**, all decisions reached there will be adopted here. But in this
PR, we don't talk about **naming, feature-creep or alternatives**.

### ⚠️ Breaking

`gitea-actions` will become a reserved user name. If a user with the
name already exists in the database, it is recommended to rename it.

### Some important reviews

- What is `DEFAULT_ACTIONS_URL` in `app.ini` for?
  - https://github.com/go-gitea/gitea/pull/21937#discussion_r1055954954
- Why the api for runners is not under the normal `/api/v1` prefix?
  - https://github.com/go-gitea/gitea/pull/21937#discussion_r1061173592
- Why DBFS?
  - https://github.com/go-gitea/gitea/pull/21937#discussion_r1061301178
- Why ignore events triggered by `gitea-actions` bot?
  - https://github.com/go-gitea/gitea/pull/21937#discussion_r1063254103
- Why there's no permission control for actions?
  - https://github.com/go-gitea/gitea/pull/21937#discussion_r1090229868

### What it looks like

<details>

#### Manage runners

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205870657-c72f590e-2e08-4cd4-be7f-2e0abb299bbf.png">

#### List runs

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205872794-50fde990-2b45-48c1-a178-908e4ec5b627.png">


#### View logs

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205872501-9b7b9000-9542-4991-8f55-18ccdada77c3.png">



</details>

### How to try it

<details>

#### 1. Start Gitea

Clone this branch and [install from
source](https://docs.gitea.io/en-us/install-from-source).

Add additional configurations in `app.ini` to enable Actions:

```ini
[actions]
ENABLED = true
```

Start it.

If all is well, you'll see the management page of runners:

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205877365-8e30a780-9b10-4154-b3e8-ee6c3cb35a59.png">


#### 2. Start runner

Clone the [act_runner](https://gitea.com/gitea/act_runner), and follow
the
[README](https://gitea.com/gitea/act_runner/src/branch/main/README.md)
to start it.

If all is well, you'll see a new runner has been added:

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205878000-216f5937-e696-470d-b66c-8473987d91c3.png">

#### 3. Enable actions for a repo

Create a new repo or open an existing one, check the `Actions` checkbox
in settings and submit.

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205879705-53e09208-73c0-4b3e-a123-2dcf9aba4b9c.png">
<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205879383-23f3d08f-1a85-41dd-a8b3-54e2ee6453e8.png">

If all is well, you'll see a new tab "Actions":

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205881648-a8072d8c-5803-4d76-b8a8-9b2fb49516c1.png">

#### 4. Upload workflow files

Upload some workflow files to `.gitea/workflows/xxx.yaml`, you can
follow the [quickstart](https://docs.github.com/en/actions/quickstart)
of GitHub Actions. Yes, Gitea Actions is compatible with GitHub Actions
in most cases, you can use the same demo:

```yaml
name: GitHub Actions Demo
run-name: ${{ github.actor }} is testing out GitHub Actions 🚀
on: [push]
jobs:
  Explore-GitHub-Actions:
    runs-on: ubuntu-latest
    steps:
      - run: echo "🎉 The job was automatically triggered by a ${{ github.event_name }} event."
      - run: echo "🐧 This job is now running on a ${{ runner.os }} server hosted by GitHub!"
      - run: echo "🔎 The name of your branch is ${{ github.ref }} and your repository is ${{ github.repository }}."
      - name: Check out repository code
        uses: actions/checkout@v3
      - run: echo "💡 The ${{ github.repository }} repository has been cloned to the runner."
      - run: echo "🖥️ The workflow is now ready to test your code on the runner."
      - name: List files in the repository
        run: |
          ls ${{ github.workspace }}
      - run: echo "🍏 This job's status is ${{ job.status }}."
```

If all is well, you'll see a new run in `Actions` tab:

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205884473-79a874bc-171b-4aaf-acd5-0241a45c3b53.png">

#### 5. Check the logs of jobs

Click a run and you'll see the logs:

<img width="1792" alt="image"
src="https://user-images.githubusercontent.com/9418365/205884800-994b0374-67f7-48ff-be9a-4c53f3141547.png">

#### 6. Go on

You can try more examples in [the
documents](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions)
of GitHub Actions, then you might find a lot of bugs.

Come on, PRs are welcome.

</details>

See also: [Feature Preview: Gitea
Actions](https://blog.gitea.io/2022/12/feature-preview-gitea-actions/)

---------

Co-authored-by: a1012112796 <1012112796@qq.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/models/actions/utils.go b/models/actions/utils.go
new file mode 100644
index 0000000000..12657942fc
--- /dev/null
+++ b/models/actions/utils.go
@@ -0,0 +1,84 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"time"
+
+	auth_model "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/modules/util"
+)
+
+func generateSaltedToken() (string, string, string, string, error) {
+	salt, err := util.CryptoRandomString(10)
+	if err != nil {
+		return "", "", "", "", err
+	}
+	buf, err := util.CryptoRandomBytes(20)
+	if err != nil {
+		return "", "", "", "", err
+	}
+	token := hex.EncodeToString(buf)
+	hash := auth_model.HashToken(token, salt)
+	return token, salt, hash, token[len(token)-8:], nil
+}
+
+/*
+LogIndexes is the index for mapping log line number to buffer offset.
+Because it uses varint encoding, it is impossible to predict its size.
+But we can make a simple estimate with an assumption that each log line has 200 byte, then:
+| lines     | file size           | index size         |
+|-----------|---------------------|--------------------|
+| 100       | 20 KiB(20000)       | 258 B(258)         |
+| 1000      | 195 KiB(200000)     | 2.9 KiB(2958)      |
+| 10000     | 1.9 MiB(2000000)    | 34 KiB(34715)      |
+| 100000    | 19 MiB(20000000)    | 386 KiB(394715)    |
+| 1000000   | 191 MiB(200000000)  | 4.1 MiB(4323626)   |
+| 10000000  | 1.9 GiB(2000000000) | 47 MiB(49323626)   |
+| 100000000 | 19 GiB(20000000000) | 490 MiB(513424280) |
+*/
+type LogIndexes []int64
+
+func (indexes *LogIndexes) FromDB(b []byte) error {
+	reader := bytes.NewReader(b)
+	for {
+		v, err := binary.ReadVarint(reader)
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				return nil
+			}
+			return fmt.Errorf("binary ReadVarint: %w", err)
+		}
+		*indexes = append(*indexes, v)
+	}
+}
+
+func (indexes *LogIndexes) ToDB() ([]byte, error) {
+	buf, i := make([]byte, binary.MaxVarintLen64*len(*indexes)), 0
+	for _, v := range *indexes {
+		n := binary.PutVarint(buf[i:], v)
+		i += n
+	}
+	return buf[:i], nil
+}
+
+var timeSince = time.Since
+
+func calculateDuration(started, stopped timeutil.TimeStamp, status Status) time.Duration {
+	if started == 0 {
+		return 0
+	}
+	s := started.AsTime()
+	if status.IsDone() {
+		return stopped.AsTime().Sub(s)
+	}
+	return timeSince(s).Truncate(time.Second)
+}