CI: Teach our Azure Pipeline to run `sparse`

[dscho]

One of the earliest open source static analyzers is sparse, and occasionally Ramsay Jones sends out mails on the Git mailing list that some function or other should be declared static because sparse found out that it is only used within the same file.

Let's add a job to our Azure Pipeline to also run sparse. There is now a build offering an Ubuntu package of sparse as build artifact: https://dev.azure.com/git/git/_build?definitionId=10&_a=summary (which can be consumed in the same way the git-sdk-64-minimal build artifact is consumed, via a PowerShell step).

See the thread around https://public-inbox.org/git/20190129014426.GC7268@google.com/ for more details.

Official documentation how to use sparse: https://kernelnewbies.org/Sparse

[sgn]

Hi @dscho,

I made a draft version for this one in sgn@ae06de1

Would you mind take a look, if it's OK, I'll send to the list.

I would like to discuss off-list first, to reduce the noise.

[dscho]

I would like to discuss off-list first, to reduce the noise.

I added some comments.

Please note, however, that I am very uncomfortable with doing this "off-list". In the least, I would like to discuss this in a proper PR, so that others can see what I suggested later without having to jump through hoops.

[sgn]

I created the PR here git#774

I replaced the call to json_pp with jq.
It's available already in both Travis and Github Action, and it's easier to read.

[dscho]

Since the subject came up on the Git mailing list again: the Bash step to download and install the sparse package would look like this:

urlbase=https://dev.azure.com/git/git/_apis/build/builds
id=$(curl "$urlbase?definitions=10&statusFilter=completed&resultFilter=succeeded&\$top=1" |
	json_pp |
	sed -n 's/^         "id" : \([1-9][0-9]*\).*/\1/p')
download_url="$(curl "$urlbase/$id/artifacts" |
	json_pp |
	sed -n '/^      {/{:1;N;/\n      }/b2;b1;:2;/"name" : "sparse"/{s/.*"downloadUrl" : "\([^"]*\).*/\1/p}}')"
curl -Lo sparse.zip "$download_url"
unzip sparse.zip
sudo dpkg -i sparse/*.deb