gitignore file is too broad

[gnprice]

BPO	37936
Nosy	@brettcannon, @zware, @gnprice, @miss-islington
PRs	bpo-37936: Avoid ignoring files that we actually do track. #15451 bpo-37936: Remove some .gitignore rules that were intended locally. #15542 [3.8] bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542) #15552 [3.7] bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542) #15553 [3.8] bpo-37936: Avoid ignoring files that we actually do track. (GH-15451) #15747 [3.7] bpo-37936: Avoid ignoring files that we actually do track. (GH-15451) #15748 bpo-37936: Systematically distinguish rooted vs. unrooted in .gitignore. #15823 [3.8] bpo-37936: Systematically distinguish rooted vs. unrooted in .gitignore (GH-15823) #15900

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-09-11.09:38:15.442>
created_at = <Date 2019-08-24.07:15:12.884>
labels = ['build', '3.8', '3.9']
title = 'gitignore file is too broad'
updated_at = <Date 2019-09-11.10:31:15.066>
user = 'https://github.com/gnprice'

bugs.python.org fields:

activity = <Date 2019-09-11.10:31:15.066>
actor = 'zach.ware'
assignee = 'none'
closed = True
closed_date = <Date 2019-09-11.09:38:15.442>
closer = 'zach.ware'
components = ['Build']
creation = <Date 2019-08-24.07:15:12.884>
creator = 'Greg Price'
dependencies = []
files = []
hgrepos = []
issue_num = 37936
keywords = ['patch']
message_count = 12.0
messages = ['350355', '350600', '350640', '350641', '350642', '351379', '351406', '351453', '351581', '351776', '351779', '351801']
nosy_count = 4.0
nosy_names = ['brett.cannon', 'zach.ware', 'Greg Price', 'miss-islington']
pr_nums = ['15451', '15542', '15552', '15553', '15747', '15748', '15823', '15900']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue37936'
versions = ['Python 3.8', 'Python 3.9']

[gnprice]

There are a number of files that we track in the repo, but are nevertheless covered by .gitignore.

This mostly doesn't change anything, because Git itself only cares what .gitignore has to say about files that aren't already tracked. But:

• It affects any new files someone might add that are covered by the same unintentionally-broad patterns. In that case it'd be likely to cause some confused debugging into why Git wasn't seeing the file; or possibly loss of work, if the person didn't notice that the file had never been committed to Git.

• More immediately, other tools that aren't Git but consult the Git ignore rules don't necessarily implement this wrinkle. In particular this is unfortunately a WONTFIX bug in ripgrep / rg: Please do not ignore file tracked by git, even it's in .gitignore BurntSushi/ripgrep#1127 .

I learned of the rg bug (and, for that matter, refreshed myself on just how Git itself handles this case) after some confusion today where I was looking with for references to a given macro, thought I'd looked at all of them... and then later noticed through git log -p -S a reference in [PC/pyconfig.h](https://github.com/python/cpython/blob/main/PC/pyconfig.h) with no subsequent change deleting it. Turned out it was indeed there and I needed to take account of it.

Here's the list of affected files:

$ git ls-files -i --exclude-standard 
.gitignore
Doc/Makefile
Lib/test/data/README
Modules/Setup
PC/pyconfig.h
Tools/freeze/test/Makefile
Tools/msi/core/core.wixproj
Tools/msi/core/core.wxs
Tools/msi/core/core_d.wixproj
Tools/msi/core/core_d.wxs
Tools/msi/core/core_en-US.wxl
Tools/msi/core/core_files.wxs
Tools/msi/core/core_pdb.wixproj
Tools/msi/core/core_pdb.wxs
Tools/unicode/Makefile

Fortunately this is not hard to fix. The semantics of .gitignore have a couple of gotchas, but once you know them it's not really any more complicated to get the behavior exactly right. And I've previously spent the hour or two to read up on it... and when I forget, I just consult my own short notes :), at the top of this file:
https://github.com/zulip/zulip/blob/master/.gitignore

I have a minimal fix which takes care of all the files above. I'll post that shortly, and I may also write up a more thorough fix that tries to make it easy not to fall into the same Git pitfall again.

[gnprice]

I have a minimal fix which takes care of all the files above. I'll post that shortly, and I may also write up a more thorough fix that tries to make it easy not to fall into the same Git pitfall again.

Both now done.

• PATH is not honored in subprocess.Popen in win32 #59656 is that minimal fix.
• Just now I've posted bpo-37936: Systematically distinguish rooted vs. unrooted in .gitignore. gnprice/cpython#1 , which is the more thorough fix. It's written on top of the minimal fix, but I could also squash them together as one PR.

Also just posted #59747 . This is a small edit, deleting some lines whose author evidently never intended them to get committed to the repo. I'd noticed those lines before and been mildly puzzled; writing up the thorough fix caused me to look in the history and see how they were added, and resolve the mystery :). I've kept that as a separate PR just to reduce the number of moving parts in the main one, because the reasoning for it is quite independent.

[miss-islington]

New changeset 8c9e9b0 by Miss Islington (bot) (Greg Price) in branch 'master':
bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542)
8c9e9b0

[miss-islington]

New changeset caf7a30 by Miss Islington (bot) in branch '3.8':
bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542)
caf7a30

[miss-islington]

New changeset 2f0440e by Miss Islington (bot) in branch '3.7':
bpo-37936: Remove some .gitignore rules that were intended locally. (GH-15542)
2f0440e

[miss-islington]

New changeset 5e5e951 by Miss Islington (bot) (Greg Price) in branch 'master':
bpo-37936: Avoid ignoring files that we actually do track. (GH-15451)
5e5e951

[miss-islington]

New changeset c837ad4 by Miss Islington (bot) in branch '3.8':
bpo-37936: Avoid ignoring files that we actually do track. (GH-15451)
c837ad4

[zware]

New changeset 9ae9ac1 by Zachary Ware (Miss Islington (bot)) in branch '3.7':
bpo-37936: Avoid ignoring files that we actually do track. (GH-15451) (GH-15748)
9ae9ac1

[gnprice]

Thanks @zach.ware for the review and merge of #59656!

That was the "minimal" fix, fixing rules that apply to files we have in the repo now. So rg will no longer ignore [PC/pyconfig.h](https://github.com/python/cpython/blob/main/PC/pyconfig.h). :-)

I've just sent #60027 with the "more thorough" fix on top of that, which tries to make it easy not to fall into the same Git pitfall again.

[zware]

New changeset 455122a by Zachary Ware (Greg Price) in branch 'master':
bpo-37936: Systematically distinguish rooted vs. unrooted in .gitignore (GH-15823)
455122a

[zware]

Ok, now it's done :)

Thanks, Greg.

[zware]

New changeset df935b5 by Zachary Ware in branch '3.8':
[3.8] bpo-37936: Systematically distinguish rooted vs. unrooted in .gitignore (GH-15823) (GH-15900)
df935b5