README.md error?

[johncblacker]

Expected behaviour

README.md instructions for building old releases (or other than current) don't seem to work
According to the README.md, to build using an older version of opencv or opencv_contrib one should
perform a git checkout of the older release from within the opencv/opencv_contrib sub directories. When
I did that, checking out version 4.5.5. I issued a git status and I'm indeed at that release in both subdirectories.

Actual behaviour

When I build the wheel with pip wheel . --verbose as directed in the README.me, it actually builds the 4.8 version instead.

Steps to reproduce

cd opencv
git checkout dad26339a975b49cfb6c7dbe4bd5276c9dcb36e2
git status
HEAD detached at dad26339a9
nothing to commit, working tree clean

cd opencv_contrib
git git rev-list -n 1 4.5.5
fatal: ambiguous argument '4.5.5': unknown revision or path not in the working tree.
git branch --all

• 4.x
  remotes/origin/3.4
  remotes/origin/33
  remotes/origin/4.x
  remotes/origin/5.x
  remotes/origin/HEAD -> origin/4.x
  remotes/origin/feat/aarch64
  remotes/origin/feat/manylinux2014
  remotes/origin/feat/python39
  remotes/origin/feat/qt5
  remotes/origin/feat/sdist
  remotes/origin/gs/test-github-actions
  remotes/origin/gs/update-3.4
  remotes/origin/gs/update-opencv-3.4-license
  remotes/origin/master

• example code
• operating system
• architecture (e.g. x86)
• opencv-python version

So, I presume opencv_contrib 4.x is sufficient and correct because there doen't appear to be a tag
for 4.5.5

I notice that at the beginning of the build process, a git submobule update --init --recursive <cmake_source_dir>
(the directory I presume is the opencv submodule subdirectory). It appears that after that command is issued a
"git checkout" results in the following:
Submodule path 'opencv': checked out 'f9a59f2592993d3dcc080e495f4f5e02dd8ec7ef'
indicating that my checkout of 4.5.5 has been overridden with the 4.8 version.

I see no instructions in the README.md indicating that I forgot to do something. So, either the 4.8 version
is somehow "baked" into the setup/config process somewhere or the git submodule update... command is the culprit
but there needs to be some way of overriding that behavior; otherwise one can't build from an older source. I have verified
that the git submodule update --init --recursive opencv command will indeed set the opencv HEAD back to version 4.8.

There needs to be either more clarity in the instructions or the process needs to be changed to allow building from older sources.

Issue submission checklist

• [ x ] This is not a generic OpenCV usage question (looking for help for coding, other usage questions, homework etc.)
• [x ] I have read the README of this repository and understand that this repository provides only an automated build toolchain for OpenCV Python packages (there is no actual OpenCV code here)
• [x ] The issue is related to the build scripts in this repository, to the pre-built binaries or is a feature request (such as "please enable this additional dependency")
• [x ] I'm using the latest version of opencv-python

[bjmcculloch]

Yes, worked the last time I used opencv-python in this way, about a year ago. It looks like this was introduced with commit 615f3df. As a workaround, in setup.py, I commented out the whole if os.path.exists(".git"): block and everything worked as expected to build an older OpenCV version.