Only run JIT formatting job if there are JIT changes

[BruceForstall]

No description provided.

[ghost]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[BruceForstall]

@dotnet/jit-contrib

[BruceForstall]

I presume this means all files in the jit directory and all subdirectories of the jit directory?

[kunalspathak]

looks like it.

[safern]

Yes. If you want to know more about how this works, here is the summary of how it works:

runtime/eng/pipelines/evaluate-changed-paths.sh

Lines 2 to 17 in d471a03

	:'
	Scenarios:
	1. exclude paths are specified
	Will include all paths except the ones in the exclude list.
	2. include paths are specified
	Will only include paths specified in the list.
	3. exclude + include:
	1st we evaluate changes for all paths except ones in excluded list. If we can not find
	any applicable changes like that, then we evaluate changes for incldued paths
	if any of these two finds changes, then a variable will be set to true.
	In order to consume this variable in a yaml pipeline, reference it via: $[ dependencies.<JobName>.outputs["<StepName>_<subset>.containschange"] ]
	Example:
	-difftarget ''HEAD^1'' -subset coreclr -includepaths ''src/libraries/System.Private.CoreLib/*'' -excludepaths ''src/libraries/*+src/installer/*''
	This example will include ALL path changes except the ones under src/libraries/*!System.Private.CoreLib/*

And this is the logic that takes care of that:

runtime/eng/pipelines/evaluate-changed-paths.sh

Lines 132 to 183 in d471a03

	probePaths() {
	local _subset=$subset_name
	local _azure_devops_var_name=$azure_variable
	local exclude_path_string=""
	local include_path_string=""
	local found_applying_changes=false
	if [[ ${#exclude_paths[@]}-gt 0 ]];then
	echo""
	echo"******* Probing $_subset exclude paths *******";
	for_pathin"${exclude_paths[@]}";do
	echo"$_path"
	if [[ "$exclude_path_string"=="" ]];then
	exclude_path_string=":!$_path"
	else
	exclude_path_string="$exclude_path_string :!$_path"
	fi
	done
	if! probePathsWithExitCode $exclude_path_string;then
	found_applying_changes=true
	printMatchedPaths $exclude_path_string
	fi
	fi
	if [[ $found_applying_changes!=true&&${#include_paths[@]}-gt 0 ]];then
	echo""
	echo"******* Probing $_subset include paths *******";
	for_pathin"${include_paths[@]}";do
	echo"$_path"
	if [[ "$include_path_string"=="" ]];then
	include_path_string=":$_path"
	else
	include_path_string="$include_path_string :$_path"
	fi
	done
	if! probePathsWithExitCode $include_path_string;then
	found_applying_changes=true
	printMatchedPaths $include_path_string
	fi
	fi
	if [[ $found_applying_changes==true ]];then
	echo""
	echo"Setting pipeline variable $_azure_devops_var_name=true"
	Write-PipelineSetVariable -name $_azure_devops_var_name -value true
	else
	echo""
	echo"No changed files for $_subset"
	fi
	}

[danmoseley]

This looks right to me but someone like @safern should OK it.