cargo init - check .gitignore before appending /target

[Mirch]

Problem

When running cargo init in an existing git repository, cargo adds a /target line to .gitignore, regardless of whether that line is already present.

Proposed Solution

After checking if the .gitignore file exists, scan the lines to search for a /target, target/ or */taget line.

Notes

cargo -vV output:

cargo 1.68.0 (115f34552 2023-02-26)
release: 1.68.0
commit-hash: 115f34552518a2f9b96d740192addbac1271e7e6
commit-date: 2023-02-26
host: aarch64-apple-darwin
libgit2: 1.5.0 (sys:0.16.0 vendored)
libcurl: 7.79.1 (sys:0.4.59+curl-7.86.0 system ssl:(SecureTransport) LibreSSL/3.3.6)
os: Mac OS 12.5.1 [64-bit]

[weihanglo]

What version did you use having that issue? Having an output of cargo -vV attached here would be nice for us to track the issue.

The feature exists from 1.33 via #6521 so far I can tell. The function format_existing does the job.

There is also a snapshot test to verify the behavior. The input is:

cargo/tests/testsuite/init/simple_git_ignore_exists/in/.gitignore

Lines 1 to 2 in 5febbe5

	/target
	**/some.file

And output be like:

cargo/tests/testsuite/init/simple_git_ignore_exists/out/.gitignore

Lines 1 to 9 in 5febbe5

	/target
	**/some.file
	# Added by cargo
	#
	# already existing elements were commented out
	#/target
	/Cargo.lock

So it looks like the issue shouldn't happen. I wonder if the entry of your /target have some trailing spaces?

[Mirch]

@weihanglo I added the cargo -vV output to the issue.

I also tried to reproduce the problem and found the following:

If /target is present, the line added by cargo init is indeed commented out. However, it looks like target/ or *target/ are not correctly identified.

The following .gitignore file is what I'm left with after creating a new repository from Github (with the Rust template for .gitignore), cloning the repo and then running cargo init:

# Generated by Cargo
# will have compiled files and executables
debug/
target/

# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
Cargo.lock

# These are backup files generated by rustfmt
**/*.rs.bk

# MSVC Windows builds of rustc generate these, which store debugging information
*.pdb


# Added by cargo

/target

[weihanglo]

Thanks for the reply. I think your reproduction is correct.

However, cargo init at this moment doesn't add an item if there is an exact-matched one. For /target, target/ and *target/, each of them has a slightly different meaning. I don't feel like Cargo should be “smarter” to ignore all of them when one exists.