Invoke-Build tasks for markdown files (using Markdown.pl)

Markdown.tasks.ps1

# Invoke-Build tasks for markdown files (using Markdown.pl)
# <https://gist.github.com/1225405>

<#
Task: Convert markdown files to HTML files (using Markdown.pl).

Requires:
* Perl script Markdown.pl <http://daringfireball.net/projects/markdown/>
* Either perl executable in the path or the predefined alias 'perl', e.g.:
	Set-Alias perl "C:\Program Files\Git\bin\perl.exe"

Inputs: Markdown files in the current location.
Outputs: *.htm files with same base names as input.
#>
task ConvertMarkdown -Partial -Inputs {Get-Item *.md, *.markdown} -Outputs {process{[System.IO.Path]::ChangeExtension($_, 'htm')}} {
	begin {
		assert (Get-Command perl -ErrorAction 0) "Command 'perl' is not found."
		$script = Get-Command Markdown.pl -ErrorAction 0
		assert $script "Script 'Markdown.pl' is not found."
		$script = $script.Definition
	}
	process {
		perl $script $_ | Set-Content -LiteralPath $2
	}
}

<#
Task: Remove HTML files presumably created by ConvertMarkdown.
All *.htm files having *.md or *.markdown pairs are removed.
#>
task RemoveMarkdownHtml {
	foreach($_ in Get-Item *.md, *.markdown) {
		$path = [System.IO.Path]::ChangeExtension($_.FullName, 'htm')
		if (Test-Path -LiteralPath $path) { Remove-Item -LiteralPath $path }
	}
}