windows: jj breaks on 'fake symlinks' generated by git

[jyn514]

Description

PS C:\Users\jyn\src\dotfiles> jj diff
ignoring symlink at \\?\C:\Users\jyn\AppData\Local\Temp\jj-diff-5II3rq\left\bin\ddg
Error: Failed to generate diff
Caused by:
1: Failed to write directories to diff
2: Failed to stat file \\?\C:\Users\jyn\AppData\Local\Temp\jj-diff-5II3rq\left\bin\ddg
3: The system cannot find the file specified. (os error 2)

mingw file shows that bin/ddg is a normal text file:

jyn@DESKTOP-TN36JV8 MINGW64 ~/src/dotfiles (master)
$ file bin/ddg
bin/ddg: ASCII text, with no line terminators

jyn@DESKTOP-TN36JV8 MINGW64 ~/src/dotfiles (master)
$ cat bin/ddg
ducker

Steps to Reproduce the Problem

i am not quite sure how to replicate this; i think you would have to create the symlink on linux, push it to a remote, and then clone it from windows with core.symlinks=false set.

Expected Behavior

jj doesn't exit with an error.

Specifications

• Platform: Windows 11
• Version: 0.14.0

[jyn514]

i think the reason jj thinks the symlink has been modified in the first place is because it doesn't respect git's core.autocrlf setting (i have it set to false) #53

[martinvonz]

Since #2996, we should at least preserve the symlink by writing them as regular files (we used to panic). The open PR #2939 adds support for writing symlinks as real symlinks when possible.

Do you clone the repo with jj git clone or regular git clone? More directly, did git or jj write the working copy? Is the issue when git has written a real symlink there and jj then tries to snapshot it?

[jyn514]

i cloned this with git clone. i assume that means git wrote the working copy.

snapshotting seems to be ok? jj status succeeds at least (it shows almost every file as modified though, because of CRLF issues). it's just jj diff that errors out.

[yuja]

Error: Failed to generate diff

This message suggest that jj diff tries to set up snapshot directories for external diff tool, which uses the same machinery as the regular working copy. So I think #2996 would fix the issue.