From: Junio C Hamano <gitster@pobox.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Han Xin" <hanxin.hx@bytedance.com>,
chiyutianyi@gmail.com, derrickstolee@github.com,
git@vger.kernel.org, haiyangtand@gmail.com,
jonathantanmy@google.com, me@ttaylorr.com, ps@pks.im
Subject: Re: [PATCH v3 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph()
Date: Fri, 01 Jul 2022 13:47:04 -0700 [thread overview]
Message-ID: <xmqq1qv48ss7.fsf@gitster.g> (raw)
In-Reply-To: <n3p471no-671q-2701-1r72-s0q02ns09053@tzk.qr> (Johannes Schindelin's message of "Fri, 1 Jul 2022 21:31:26 +0200 (CEST)")
Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> Whenever you call a non-MSYS program from an MSYS program (and remember,
> an MSYS program is a program that uses the MSYS2 runtime that acts as a
> POSIX emulation layer), "magic" things are done. In our context,
> `bash.exe` is an MSYS program, and the non-MSYS program that is called is
> `git.exe`.
>
> So what are those "magic" things? The command-line arguments and the
> environment variables are auto-converted: everything that looks like a
> Unix-style path (or path list, like the `PATH` environment variable) is
> converted to a Windows-style path or path list (on Windows, the colon
> cannot be the separator in `PATH`, therefore the semicolon is used).
>
> And this is where it gets _really_ tricky to explain what is going on:
> what _does_ look like a Unix-style path? The exact rules are convoluted
> and hard to explain, but they work _most of the time_. For example,
> `/usr/bin:/hello` is converted to `C:\Program Files\Git\usr\bin;C:\Program
> Files\Git\hello` or something like that. But `kernel.org:/home/gitster` is
> not, because it looks more like an SSH path. Similarly, `C:/Program Files`
> is interpreted as a Windows-style path, even if it could technically be a
> Unix-style path list.
>
> Now, if you call `git.exe -C /blabla <command>`, it works, because
> `git.exe` is a non-MSYS program, therefore that `/blabla` is converted to
> a Windows-style path before executing `git.exe`. However, when you write a
> file via `echo /blabla >file`, that `echo` is either the Bash built-in, or
> it is an MSYS program, and no argument conversion takes place. If you
> _then_ ask `git.exe` to read and interpret the file as a path, it won't
> know what to do with that Unix-style path.
>
> You can substitute `$PWD` for `/blabla` in all of this, and it will hold
> true just the same.
>
> So what makes `pwd` special?
>
> Well, `pwd.exe` itself is an MSYS program, so it would still report a path
> that `git.exe` cannot understand. But in Git's test suite, we specifically
> override `pwd` to be a shell function that calls `pwd.exe -W`, which does
> output Windows-style paths.
>
> The thing that makes that `GIT_*=$PWD git ...` call work is that the
> environment is automagically converted because `git` is a non-MSYS
> program. The thing that makes `echo $PWD >.git/objects/info/alternates`
> not work is that `echo` _is_ an MSYS program (or Bash built-in, which is
> the same thing here, for all practical purposes), so it writes the path
> verbatim into that file, but then we expect `git.exe` to read this file
> and interpret it as a list of paths.
----- 8< --------- 8< --------- 8< --------- 8< --------- 8< -----
> Hopefully that clarifies the scenario a bit, even if it is far from a
> concise explanation (I did edit this mail multiple times for clarity and
> brevity, though, as I do with pretty much all of my mails).
Certainly it does help. Thanks.
I wonder if it makes sense to keep a copy of the bulk of your
response in t/ somewhere, and refer to it from t/README, to help
fellow non-Windows developers to avoid breaking tests on Windows
without knowing.
next prev parent reply other threads:[~2022-07-01 20:47 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 7:25 An endless loop fetching issue with partial clone, alternates and commit graph Haiyng Tan
2022-06-15 2:18 ` Taylor Blau
2022-06-16 3:38 ` [RFC PATCH 0/2] " Han Xin
2022-06-16 3:38 ` [RFC PATCH 1/2] commit-graph.c: add "flags" to lookup_commit_in_graph() Han Xin
2022-06-16 3:38 ` [RFC PATCH 2/2] fetch-pack.c: pass "oi_flags" " Han Xin
2022-06-17 21:47 ` [RFC PATCH 0/2] Re: An endless loop fetching issue with partial clone, alternates and commit graph Jonathan Tan
2022-06-18 3:01 ` [PATCH v1] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-20 7:07 ` Patrick Steinhardt
2022-06-20 8:53 ` [External] " 欣韩
2022-06-20 9:05 ` Patrick Steinhardt
2022-06-21 18:23 ` Jonathan Tan
2022-06-22 3:17 ` Han Xin
2022-06-24 5:27 ` [PATCH v2 0/2] " Han Xin
2022-06-24 5:27 ` [PATCH v2 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-24 16:03 ` Junio C Hamano
2022-06-25 1:35 ` Han Xin
2022-06-27 12:22 ` Junio C Hamano
2022-06-24 5:27 ` [PATCH v2 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-24 16:56 ` Junio C Hamano
2022-06-25 2:25 ` Han Xin
2022-06-25 2:31 ` Han Xin
2022-06-28 2:02 ` [PATCH v3 0/2] " Han Xin
2022-06-28 2:02 ` [PATCH v3 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-28 2:02 ` [PATCH v3 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-28 7:49 ` Ævar Arnfjörð Bjarmason
2022-06-28 17:36 ` Junio C Hamano
2022-06-30 12:21 ` Johannes Schindelin
2022-06-30 13:43 ` Ævar Arnfjörð Bjarmason
2022-06-30 15:40 ` Junio C Hamano
2022-06-30 18:47 ` Ævar Arnfjörð Bjarmason
2022-07-01 19:31 ` Johannes Schindelin
2022-07-01 20:47 ` Junio C Hamano [this message]
2022-06-29 2:08 ` Han Xin
2022-06-30 17:37 ` test name conflict + js/ci-github-workflow-markup regression (was: [PATCH v3 0/2] no lazy fetch in lookup_commit_in_graph()) Ævar Arnfjörð Bjarmason
2022-07-01 1:34 ` [PATCH v4 0/1] no lazy fetch in lookup_commit_in_graph() Han Xin
2022-07-01 1:34 ` [PATCH v4 1/1] commit-graph.c: " Han Xin
2022-07-09 12:23 ` Michael J Gruber
2022-07-11 15:09 ` Jeff King
2022-07-11 20:17 ` Junio C Hamano
2022-07-12 1:52 ` [External] " Han Xin
2022-07-12 5:23 ` Junio C Hamano
2022-07-12 5:32 ` Han Xin
2022-07-12 6:37 ` [External] " Jeff King
2022-07-12 14:19 ` Junio C Hamano
2022-07-12 6:50 ` [PATCH v5 0/1] " Han Xin
2022-07-12 6:50 ` [PATCH v5 1/1] commit-graph.c: " Han Xin
2022-07-12 9:50 ` Ævar Arnfjörð Bjarmason
2022-07-13 1:26 ` Han Xin
2022-07-12 6:58 ` [PATCH v5 0/1] " Jeff King
2022-07-12 8:01 ` [PATCH v1] t5330: remove run_with_limited_processses() Han Xin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=xmqq1qv48ss7.fsf@gitster.g \
--to=gitster@pobox.com \
--cc=Johannes.Schindelin@gmx.de \
--cc=avarab@gmail.com \
--cc=chiyutianyi@gmail.com \
--cc=derrickstolee@github.com \
--cc=git@vger.kernel.org \
--cc=haiyangtand@gmail.com \
--cc=hanxin.hx@bytedance.com \
--cc=jonathantanmy@google.com \
--cc=me@ttaylorr.com \
--cc=ps@pks.im \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).