Release fails if there are no changes to gh-pages branch

[brad]

Use case: My azure setup builds on every merge to master and releases on every master build. If I merge in a change to a readme file or .gitignore or something else that results in no changes to HTML, the release will fail. It would be nice if this situation doesn't cause the task to fail. The logs:

2018-11-15T05:25:47.6589352Z ##[section]Starting: Publishes to GitHub Pages
2018-11-15T05:25:47.6594060Z ==============================================================================
2018-11-15T05:25:47.6594159Z Task         : Publish to GitHub Pages
2018-11-15T05:25:47.6594218Z Description  : Publishes files to a GitHub Pages gh-pages branch
2018-11-15T05:25:47.6594270Z Version      : 0.13.0
2018-11-15T05:25:47.6594334Z Author       : James Randall
2018-11-15T05:25:47.6594382Z Help         : 
2018-11-15T05:25:47.6594451Z ==============================================================================
2018-11-15T05:25:48.7385928Z Cloning existing GitHub Pages branch
2018-11-15T05:25:53.1698006Z Copying new documentation into branch
2018-11-15T05:25:53.2787015Z Committing the GitHub Pages Branch
2018-11-15T05:25:53.4661368Z On branch gh-pages
2018-11-15T05:25:53.4662152Z Your branch is up to date with 'origin/gh-pages'.
2018-11-15T05:25:53.4662393Z 
2018-11-15T05:25:53.4662676Z nothing to commit, working tree clean
2018-11-15T05:25:53.4791413Z ##[error]Error committing - see earlier log, error code 1
2018-11-15T05:25:55.7297391Z ##[error]Exit code 1 returned from process: file name 'C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe', arguments '-NoLogo -Sta -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command ". ([scriptblock]::Create('if (!$PSHOME) { $null = Get-Item -LiteralPath ''variable:PSHOME'' } else { Import-Module -Name ([System.IO.Path]::Combine($PSHOME, ''Modules\Microsoft.PowerShell.Management\Microsoft.PowerShell.Management.psd1'')) ; Import-Module -Name ([System.IO.Path]::Combine($PSHOME, ''Modules\Microsoft.PowerShell.Utility\Microsoft.PowerShell.Utility.psd1'')) }')) 2>&1 | ForEach-Object { Write-Verbose $_.Exception.Message -Verbose } ; Import-Module -Name 'D:\_work\_tasks\GitHubPagesPublish_65386086-c58c-4396-bc83-4c7a39e84448\0.13.0\ps_modules\VstsTaskSdk\VstsTaskSdk.psd1' -ArgumentList @{ NonInteractive = $true } -ErrorAction Stop ; $VerbosePreference = 'SilentlyContinue' ; $DebugPreference = 'SilentlyContinue' ; Invoke-VstsTaskScript -ScriptBlock ([scriptblock]::Create('. ''D:\_work\_tasks\GitHubPagesPublish_65386086-c58c-4396-bc83-4c7a39e84448\0.13.0\publish.ps1'''))"'.
2018-11-15T05:25:55.7302520Z ##[section]Finishing: Publishes to GitHub Pages

[JamesRandall]

Thanks for the PR - I'll get that merged and released shortly!

[brad]

No problem, thanks for the task!