[PATCH] ci(windows): ensure that we do not pick up random executables

From: Johannes Schindelin <johannes.schindelin@gmx.de>

On the Windows build agents, a lot of programs are installed, and added to the PATH automatically.

One such program is Git for Windows, and due to the way it is set up, unfortunately its copy of `gpg.exe` is also reachable via the PATH.

This usually does not pose any problems. To the contrary, it even allows us to test the GPG parts of Git's test suite even if `gpg.exe` is not delivered as part of `git-sdk-64-minimal`, the minimal subset of Git for Windows' SDK that we use in the CI builds to compile Git.

However, every once in a while we build a new MSYS2 runtime, which means that there is a mismatch between the copy in `git-sdk-64-minimal` and the copy in C:\Program Files\Git\usr\bin. When that happens we hit the dreaded problem where only one `msys-2.0.dll` is expected to be in the PATH, and things start to fail.

Let's avoid all of this by restricting the PATH to the minimal set. This is actually done by `git-sdk-64-minimal`'s `/etc/profile`, and we just have to source this file manually (one would expect that it is sourced automatically, but the Bash steps in Azure Pipelines/GitHub workflows are explicitly run using `--noprofile`, hence the need for doing this explicitly).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
    ci(windows): avoid using external gpg by mistake
    
    I stumbled over a CI failure this morning when I scrambled to tie up all
    the loose ends for an unexpected v2.33.1 release. Turns out that the CI
    picked up the installed Git for Windows' gpg.exe, and due to a (new, as
    of this morning) mismatch in the MSYS2 runtime between the installed Git
    for Windows and the subset of the Git for Windows SDK used for compiling
    in the CI runs, it worked just enough to pass the prereq, but then
    failed the tests.
    
    Seeing as essentially every single CI build will fail without this patch
    right up until the point in time when Git for Windows is upgraded in the
    build agents (to a version that does yet exist), it would be good to
    fast-track this to maint.
    
    Note: I based this on the earliest topic where it would apply without
    merge conflicts, js/ci-windows-update (which is unfortunately quite
    recent, it is not reachable from any version older than v2.33.0).

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1057%2Fdscho%2Fwork-around-windows-ci-failures-with-gpg-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1057/dscho/work-around-windows-ci-failures-with-gpg-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1057

 .github/workflows/main.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)