How to 'build-from-source' from a specific checkout, not HEAD?

[edrozenberg]

I'm trying to git bisect midnight-commander (mc). The 4.8.25 release works fine on Mac, 4.8.26 is partially broken (does not launch in any dir other than homedir). Want to figure out which commit broke it so I have some chance of getting the mc project to look at it.

I tried but cannot figure out any way to brew install --build-from-source from a specific git tag/checkout, and not --HEAD.

For ex. I'd want to force brew to build from a directory I create using git clone --depth 1 <repo_url>; cd <git dir>; git reset --hard <COMMIT-SHA-ID>

It seems currently there's no way to tell brew to just build the source from where it tell it, instead of having it do its own HEAD checkout.

[SMillerDev]

You can specify a git url + revision as the URL and rebuild it normally. Normally we also use a tag in that structure but it's not required.

[SMillerDev]

You need to change the default URL, see for example:
https://github.com/Homebrew/homebrew-core/blob/master/Formula/acmetool.rb#L4-L6

[edrozenberg]

@SMillerDev thanks, tried but failed. I'll give up on this approach for now. Maybe "someday" I'll send a PR for a built-in brew feature that makes it easy to build from source a specific tag/release/commit.

For reference tried modifying as below:

class MidnightCommander < Formula
  desc "Terminal-based visual file manager"
  homepage "https://www.midnight-commander.org/"
  url "https://github.com/MidnightCommander/mc.git",
      revision: "171957980e17331d6b7dab6a343db9e1f3fef49c"
  license "GPL-3.0-or-later"

brew install --build-from-source mc
Error: invalid attribute for formula 'midnight-commander': version (nil)

[Rylan12]

Since there's no tag, Homebrew doesn't know how to automatically extract the version so you'll need to specify it yourself with a version spec. Since you're just doing some testing it probably doesn't matter much what you set it to.

class MidnightCommander < Formula
  desc "Terminal-based visual file manager"
  homepage "https://www.midnight-commander.org/"
  url "https://github.com/MidnightCommander/mc.git",
      revision: "171957980e17331d6b7dab6a343db9e1f3fef49c"
  # I chose "4.8.26" because that's the latest stable version but you
  # could also choose e.g. "1.0.0" or whatever you want
  version "4.8.26"
  license "GPL-3.0-or-later"

[edrozenberg]

@Rylan12 thanks, very helpful! Sounds like the version is whatever you want it to be so I guess I could set it to something like 20200123_1234567 (matching the date/hash of the commit I'm using).

Meanwhile I took the manual build approach & w/git bisect and found the "bad" commit - related to the mc subshell. My short term workaround is mc --nosubshell to avoid whatever the subshell issue is, and I'll need to submit the issue to the mc project and see if they'll take it up.

[Rylan12]

@Rylan12 thanks, very helpful! Sounds like the version is whatever you want it to be so I guess I could set it to something like 20200123_1234567 (matching the date/hash of the commit I'm using).

Yeah, it matters more for when you're creating an actual formula to be distributed (in which case you should be using a tag not just a revision so you won't have the issue) but if you're just testing a formula out it can be whatever. You have no idea how many test formulae called "foo" I've made... 😅

[carlocab]

This seems like a really painful way of doing it, as there are a few hundred commits in between release tags. I suggest building outside of brew so you can at least make use of git bisect.

[edrozenberg]

@carlocab thanks, probably the right way to go. I'll have to "reverse engineer" what the brew mc formula does for the source build (config params, an ENV tweak, etc). Lot of experience building stuff on Linux, not much on Mac. I'll figure it out eventually.

[carlocab]

The build flags you can see in the formula. The only other important thing that brew does silently should be equivalent to

export PKG_CONFIG_PATH="$(brew --prefix openssl@1.1)/lib/pkgconfig"

It would also be good to know if this workaround is still needed:

ENV["ac_cv_func_utimensat"] = "no" if MacOS.version >= :high_sierra

[edrozenberg]

@carlocab thanks again. Tried one build with and without setting ENV["ac_cv_func_utimensat"] - doesn't make a difference to this particular problem. Maybe it's required to fix something else - I don't know what the original intent of that tweak was.

According to git bisect mc was broken sometime 4.8.25 and 4.8.26 by the following commit:

ff0fc17ae3c88128801644f7ff5f4628881206f6 is the first bad commit
commit ff0fc17ae3c88128801644f7ff5f4628881206f6
Author: Eric Roberts <ericmrobertsdeveloper@gmail.com>
Date:   Sat Sep 19 11:58:51 2020 +0300

    Ticket #4114: implement persistent command line buffer for subshell.

I'll have to report it to the mc project and see if there's something they can do about it (their level of caring about MacOS is unknown, hopefully they care...).

Used the following build script:

#!/usr/local/bin/bash

# Set var suggested on HomeBrew discussion board
export PKG_CONFIG_PATH="$(brew --prefix openssl@1.1)/lib/pkgconfig"

# Setting used by homebrew's formula
export ac_cv_func_utimensat="no"

# Go to the source
cd ~/Developer/External/mc

# Get short commit hash
hash=`git rev-parse --short=7 HEAD`

# Clean the source
make clean

# Bootstrap the source
./autogen.sh

# Configure the source
./configure                                                  \
  --disable-dependency-tracking                              \
  --disable-silent-rules                                     \
  --prefix=/usr/local/Cellar/midnight-commander/HEAD-${hash} \
  --without-x                                                \
  --with-screen=slang                                        \
  --enable-vfs-sftp

# Compile and install
make
make install

And my bisect session:

cd ~/Developer/External/mc
$ git bisect start
$ git bisect bad                           (HEAD-9436bd1)
$ git bisect good tags/4.8.25              (HEAD-1719579)
$ git bisect bad                           (HEAD-6f96cad)
$ git bisect bad                           (HEAD-2225af8)
$ git bisect bad                           (HEAD-2dc692c)
$ git bisect bad                           (HEAD-09473d8)
$ git bisect good                          (HEAD-794f94c)
$ git bisect bad                           (HEAD-c22387d)
$ git bisect good                          (HEAD-f63be5a)
$ git bisect bad                           (HEAD-ff0fc17)

[edrozenberg]

Problem is subshell related, because if I launch as mc --nosubshell in any directory as a normal user it launches instantly (as it should), but then there's no shell available with ctrl-o.