Re: [PATCH v7 0/3] RUNTIME_PREFIX relocatable Git

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Mar 26, 2018, 21:16 UTC
Message-ID: <nycvar.QRO.7.76.6.1803262305010.77@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz>
In-Reply-To: <CAD1RUU-oUXx+mGUe6QuTawLhLz1nGFZiOWnF7=DVA1uf455zfw@mail.gmail.com>

Hi,

On Mon, 26 Mar 2018, Daniel Jacques wrote:

Show 12 quoted lines

> On Mon, Mar 26, 2018 at 2:01 AM Junio C Hamano <gitster@pobox.com> wrote:
> 
> > I wonder if the relocatable Git would allow a simpler arrangement to
> > test without installing.
> 
> > I am asking merely out of curiosity, not suggesting to make a trial
> > install somewhere in the build area and run the built Git normally
> > without GIT_EXEC_PATH trick.
> 
> RUNTIME_PREFIX resolves paths relative to the runtime path of the Git
> binary. These path expectations are constructed around installation
> directories, so I'd expect that installation is a prerequisite of testing.

Indeed. This is the relevant part of the code:

        if (!prefix &&
            !(prefix = strip_path_suffix(argv0_path, GIT_EXEC_PATH)) &&
            !(prefix = strip_path_suffix(argv0_path, BINDIR)) &&
            !(prefix = strip_path_suffix(argv0_path, "git"))) {
                prefix = FALLBACK_RUNTIME_PREFIX;
                trace_printf("RUNTIME_PREFIX requested, "
                                "but prefix computation failed.  "
                                "Using static fallback '%s'.\n", prefix);
        }

Note how the argv0_path (which is the absolute path of the directory *containing* the `git` executable) is tested for several suffixes, i.e. trailing directories, namely

	libexec/git-core
	bin
	git

That means that you will have to have your `git` executable built in a worktree whose absolute path ends in one of these.

While writing this reply, I was wondering why "git" is included in this list. You know, I can see libexec/git-core and bin because that is where the `git` executable is installed to (or hard-linked to). But "git"?

Turns out that I am the responsible person for that (024aa7d8d51 (system_path(): simplify using strip_path_suffix(), and add suffix "git", 2009-02-19)), having assumed back then that everybody who uses the RUNTIME_PREFIX feature and works on Git does so in /git/. Which is of course no longer true in general. For example, I myself got bitten by this when developing some patches on top of Dan's patch series in a *linked worktree* of the name "runtime-prefix". Oh well.

But the short answer is: no, you cannot rely on the RUNTIME_PREFIX feature for running Git's own test suite. The GIT_EXEC_PATH method to force Git's test suite to use the compiled executables is still required.

Even if it is fragile: if git-FOO exists in <prefix>/bin/ and some test relies on the FOO subcommand but we removed it from the source code to test whether it is needed, the test suite would pass just fine because it finds git-FOO in the PATH.

*sigh* seems that I cannot write short answers.

Ciao, Dscho