现在不建议使用setenv。建议使用环境文件。基于@youjin的回答，同时仍然允许功能/分支(用-替换所有/的出现)，我现在使用这个:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Get branch name (merge)
        if: github.event_name != 'pull_request'
        shell: bash
        run: echo "BRANCH_NAME=$(echo ${GITHUB_REF#refs/heads/} | tr / -)" >> $GITHUB_ENV

      - name: Get branch name (pull request)
        if: github.event_name == 'pull_request'
        shell: bash
        run: echo "BRANCH_NAME=$(echo ${GITHUB_HEAD_REF} | tr / -)" >> $GITHUB_ENV

      - name: Debug
        run: echo ${{ env.BRANCH_NAME }}

同时处理pull_request和push事件的解决方案。由于set-env已弃用，因此实现了保存获得的分支名称以供后续步骤使用的变通方法。 不需要第三方操作。

name: CI
on: [ pull_request, push ]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: "Get branch name and save to env"
        env:
          IS_PR: ${{ github.EVENT_NAME == 'pull_request' }}
        run: |
          if ${IS_PR}; then
            BRANCH_NAME="${GITHUB_HEAD_REF}"
          else
            BRANCH_NAME="${GITHUB_REF##*/}"
          fi
          echo "BRANCH_NAME=${BRANCH_NAME}" >> $GITHUB_ENV

      - name: "Another step uses branch name"
        run: echo "Branch name is ${{ env.BRANCH_NAME }}"

GitHub动作中的运行时变量

${{ github.ref_name }}

至少对推送来说还行。参见ref_name了解更多细节。它说:

触发工作流运行的分支或标记名称。

对于那些刚刚找到这个线程，你现在可以使用GITHUB_REF_NAME例如${{github。ref_name}}。https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables

因此，如果你触发的操作工作流分支是main，这个变量将被设置为main。例如，如果你有多个带有发行版和主要分支的回购，这就很有用。

更新

GitHub现在支持GITHUB_REF_NAME，它代表触发工作流运行的分支或标记名称。

GitHub文档在这个https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables上

我相信GITHUB_REF是唯一包含分支名称的环境变量。

你可以从字符串的其余部分提取分支名称，如下所示:

${GITHUB_REF##*/}

例子:

$ GITHUB_REF=refs/heads/feature-branch-1
$ echo ${GITHUB_REF##*/}
feature-branch-1

更新:添加了一个完整的工作流示例。

工作流

name: CI
on: push
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Git checkout
        uses: actions/checkout@v1
      - name: Branch name
        run: echo running on branch ${GITHUB_REF##*/}
      - name: Build
        run: docker build -t tedmiston/tag-example:${GITHUB_REF##*/} .

来源:https://github.com/tedmiston/x/blob/master/.github/workflows/workflow.yml

示例输出-主分支

Run docker build -t tedmiston/tag-example:${GITHUB_REF##*/} .
  docker build -t tedmiston/tag-example:${GITHUB_REF##*/} .
  shell: /bin/bash -e {0}
Sending build context to Docker daemon  146.9kB

Step 1/1 : FROM alpine
latest: Pulling from library/alpine
9d48c3bd43c5: Pulling fs layer
9d48c3bd43c5: Verifying Checksum
9d48c3bd43c5: Download complete
9d48c3bd43c5: Pull complete
Digest: sha256:72c42ed48c3a2db31b7dafe17d275b634664a708d901ec9fd57b1529280f01fb
Status: Downloaded newer image for alpine:latest
 ---> 961769676411
Successfully built 961769676411
Successfully tagged tedmiston/tag-example:master

日志:https://github.com/tedmiston/x/commit/cdcc58a908e41d3d90c39ab3bf6fef1ad2c4238a/checks一步:16

示例输出-非主分支

Run docker build -t tedmiston/tag-example:${GITHUB_REF##*/} .
  docker build -t tedmiston/tag-example:${GITHUB_REF##*/} .
  shell: /bin/bash -e {0}
Sending build context to Docker daemon  144.9kB

Step 1/1 : FROM alpine
latest: Pulling from library/alpine
9d48c3bd43c5: Pulling fs layer
9d48c3bd43c5: Verifying Checksum
9d48c3bd43c5: Download complete
9d48c3bd43c5: Pull complete
Digest: sha256:72c42ed48c3a2db31b7dafe17d275b634664a708d901ec9fd57b1529280f01fb
Status: Downloaded newer image for alpine:latest
 ---> 961769676411
Successfully built 961769676411
Successfully tagged tedmiston/tag-example:branch-name-test

日志:https://github.com/tedmiston/x/commit/4e8d31259f861aaa2c30375756fc081c3659bddf/checks一步:16

有关参数展开语法的更多信息，请参阅这个答案。

作为参考，GitHub Actions的虚拟环境页面列出了执行环境中可用的所有环境变量。