Failed to push charts with index when multiple charts are being updated

[tomhuang12]

Describe the bug
YACR fails to upload charts tarball to gh-pages branch when multiple charts are being released due to push conflict. I think it is due to pushing to remote for every package and when second package is being pushed, remote is already ahead of local work dir. https://github.com/stecky/yet-another-chart-releaser/blob/e599f1d5dbd5364830b7232454b12e98aba44797/pkg/releaser/releaser.go#L345-L367

To Reproduce
Steps to reproduce the behavior:
Action configuration:

      - name: Run chart-releaser
        uses: stecky/yet-another-chart-releaser-action@v1
        with:
          charts_dir: charts
          charts_repo_url: xxx
          packages_with_index: true
        env:
          YACR_TOKEN: "${{ secrets.TOKEN }}"

Have charts/chart1 and charts/chart2 both updated.
See error in actions tab

Expected behavior
All packages that are being released should be pushed without any issues.

Logs

Run stecky/yet-another-chart-releaser-action@v1
Run owner=$(cut -d '/' -f 1 <<< "$GITHUB_REPOSITORY")
Looking up latest tag...
Discovering changed charts since 'xxx'...
Installing yacr v0.4.4...
Adding yacr directory to PATH...
Packaging chart 'xxx'...
Successfully packaged chart in /home/runner/work/xxx and saved it to: .yacr-release-packages/xxx.tgz
Packaging chart 'xxx'...
Successfully packaged chart in /home/runner/work/xxx and saved it to: .yacr-release-packages/xxx.tgz
Packaging chart 'xxx'...
Successfully packaged chart in /home/runner/work/xxx and saved it to: .yacr-release-packages/xxx.tgz
Releasing charts...
Preparing worktree (detached HEAD a5e0099)
HEAD is now at a5e0099 Update index.yaml
[detached HEAD 98bff8b] Publishing chart package for xxx
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 xxx.tgz
Pushing to branch "gh-pages"
To https://github.com/xxx
   a5e0099..98bff8b  HEAD -> gh-pages
Executing command git [push ***github.com/xxx HEAD:refs/heads/gh-pages]Preparing worktree (detached HEAD a5e0099)
HEAD is now at a5e0099 Update index.yaml
[detached HEAD 9ca2ae8] Publishing chart package for xxx
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 xxx.tgz
Pushing to branch "gh-pages"
To https://github.com/xxx
 ! [rejected]        HEAD -> gh-pages (non-fast-forward)
error: failed to push some refs to 'https://github.com/xxx'
hint: Updates were rejected because a pushed branch tip is behind its remote
hint: counterpart. Check out this branch and integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
Error: exit status 1
Usage:
  yet-another-chart-releaser upload [flags]

Flags:
  -c, --commit string                  Target commit for release
  -b, --git-base-url string            GitHub Base URL (only needed for private GitHub) (default "https://api.github.com/")
  -r, --git-repo string                GitHub repository
  -u, --git-upload-url string          GitHub Upload URL (only needed for private GitHub) (default "https://uploads.github.com/")
  -h, --help                           help for upload
  -o, --owner string                   GitHub username or organization
  -p, --package-path string            Path to directory with chart packages (default ".yacr-release-packages")
      --packages-with-index            Save a copy of the package files to the GitHub Pages branch
      --pages-branch string            The GitHub pages branch (default "gh-pages")
      --pr                             Create a pull request for index.yaml against the GitHub Pages branch (must not be set if --push is set)
      --push                           Push index.yaml to the GitHub Pages branch (must not be set if --pr is set)
      --release-name-template string   Go template for computing release names, using chart metadata (default "{{ .Name }}-{{ .Version }}")
      --remote string                  The Git remote used when creating a local worktree for the GitHub Pages branch (default "origin")
      --skip-existing                  Skip upload if release exists
  -t, --token string                   GitHub Auth Token

Global Flags:
      --config string   config file (default is $HOME/.yet-another-chart-releaser.yaml)

Error: exit status 1
Executing command git [push ***github.com/xxx HEAD:refs/heads/gh-pages]
Error: Process completed with exit code 1.

[annabarnes1138]

Unfortunately I don't have the time right now to fix this. If you want to submit a pull request I am happy to merge it. I would also be open to transferring the repo.