rev-parse doesn't take pwd into consideration

Hello,

I was frustrated for some minutes trying to get the HEAD version of a file, as is in the documentation. Using git's source as an example: git/Documentation$ git show HEAD:docbook.xsl fatal: ambiguous argument 'HEAD:docbook.xsl': unknown revision or path not in the working tree. Use '--' to separate paths from revisions

<hmmm>

$ git show HEAD -- docbook.xsl <nil> $

Seeing in the documentation that the parsing was made by git-rev-parse, I tried running git-rev-parse directly, ending with the same error.

I tried with the full path, just in case, but it didn't work also ($PWD/docbook.xsl).

Until finally I tried the absolute path as git is concerned, and it worked.

It works anywhere: git$ git show HEAD:Documentation/docbook.xsl <contents> git/Documentation$ git show HEAD:Documentation/docbook.xsl <contents> ...

Is it difficult to make rev-parse accept relative path specifications?