Re: [PATCH] checkpatch.pl: warn on invalid commit hash

[Joe Perches <joe@perches.com>]

On Thu, 2019-07-11 at 01:19 +0200, Matteo Croce wrote:
> It can happen that a commit message refers to an invalid hash, because
> the referenced hash changed following a rebase, or simply by mistake.
> Add a check in checkpatch.pl which checks that an hash referenced by a Fixes
> tag or just cited in the commit message is a valid commit hash.

Hi Matteo

>     $ scripts/checkpatch.pl <<'EOF'
>     Subject: [PATCH] test commit
> 
>     Sample test commit to test checkpatch.pl
>     Commit 1da177e4c3f4 ("Linux-2.6.12-rc2") really exists,
>     commit 0bba044c4ce7 ("tree") is valid but not a commit,
>     while commit b4cc0b1c0cca ("unknown") is invalid.
> 
>     Fixes: f0cacc14cade ("unknown")
>     Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>     EOF
>     WARNING: Invalid hash 0bba044c4ce7
>     WARNING: Invalid hash b4cc0b1c0cca
>     WARNING: Invalid hash f0cacc14cade
>     total: 0 errors, 3 warnings, 4 lines checked

[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -2898,6 +2898,13 @@ sub process {
>  			}
>  		}
>  
> +# check for invalid hashes
> +		if ($in_commit_log && $line =~ /(^fixes:|commit)\s+([0-9a-f]{6,40})\b/i) {
> +			if (`git cat-file -t $2 2>/dev/null` ne "commit\n") {
> +				WARN('INVALID_COMMIT_HASH', "Invalid commit hash $2");

This seems fine as a concept, but this should use a
'\n' and . $herecurr like:

> 				WARN('INVALID_COMMIT_HASH', "Invalid commit hash $2\n" . $herecurr);

And while a single quote around the identifier works, please
use the double quote style like all the other uses of WARN.

Maybe call it "UNKNOWN_COMMIT_ID" too as it might be valid
for someone else's tree that has not yet been pulled and all
other references in checkpatch use ID rather than hash.

				WARN("UNKNOWN_COMMIT_HASH",
				     "Unknown commit id '$2', maybe rebased or not pulled?\n" . $herecurr);

Finally, why wouldn't the existing git_commit_info subroutine
be used instead of an independent 'git cat-file' which may not
even run if git is not available?

Perhaps use something like:

		my $id;
		my $description;
		($id, $description) = git_commit_info($2, undef, undef);
		if (!defined($id)) {
			WARN(etc...);
		}