[PATCH] gitattributes.txt: mention exceptions to gitignore rules

[PATCH] gitattributes.txt: mention exceptions to gitignore rules

[Nguyễn Thái Ngọc Duy]

gitattr and .gitignore are supposed to use the same rules for matching
patterns. Unfortunately it's not exactly the same in reality. Mention
the differences so users won't be surprised, until gitattr gets
updates.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 2011/1/4 Marcin Wiśnicki <mwisnicki@gmail.com>:
 > I think that for the time being at least the manual page must change to
 > reflect reality.

 Looks like changes will be more than just a few lines because path_matches()
 needs to learn about directories (iow less likely to get fixed right away).
 So, yes, good idea.

 I skimmed through excluded_from_list() (gitignore) and path_matches (gitattr).
 Seems no other differences.

 Documentation/gitattributes.txt |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 5a7f936..cfaf107 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -56,6 +56,7 @@ When more than one pattern matches the path, a later line
 overrides an earlier line.  This overriding is done per
 attribute.  The rules how the pattern matches paths are the
 same as in `.gitignore` files; see linkgit:gitignore[5].
+However patterns that end with a slash is not supported.
 
 When deciding what attributes are assigned to a path, git
 consults `$GIT_DIR/info/attributes` file (which has the highest
-- 
1.7.3.4.878.g439c7

Re: [PATCH] gitattributes.txt: mention exceptions to gitignore rules

[Michael J Gruber]

Nguyễn Thái Ngọc Duy venit, vidit, dixit 04.01.2011 14:31:
> gitattr and .gitignore are supposed to use the same rules for matching
> patterns. Unfortunately it's not exactly the same in reality. Mention
> the differences so users won't be surprised, until gitattr gets
> updates.
> 
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  2011/1/4 Marcin Wiśnicki <mwisnicki@gmail.com>:
>  > I think that for the time being at least the manual page must change to
>  > reflect reality.
> 
>  Looks like changes will be more than just a few lines because path_matches()
>  needs to learn about directories (iow less likely to get fixed right away).
>  So, yes, good idea.
> 
>  I skimmed through excluded_from_list() (gitignore) and path_matches (gitattr).
>  Seems no other differences.
> 
>  Documentation/gitattributes.txt |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
> index 5a7f936..cfaf107 100644
> --- a/Documentation/gitattributes.txt
> +++ b/Documentation/gitattributes.txt
> @@ -56,6 +56,7 @@ When more than one pattern matches the path, a later line
>  overrides an earlier line.  This overriding is done per
>  attribute.  The rules how the pattern matches paths are the
>  same as in `.gitignore` files; see linkgit:gitignore[5].
> +However patterns that end with a slash is not supported.

+However, patterns terminated by a slash are not supported.

>  
>  When deciding what attributes are assigned to a path, git
>  consults `$GIT_DIR/info/attributes` file (which has the highest

Cheers,
Michael

Re: [PATCH] gitattributes.txt: mention exceptions to gitignore rules

[Marcin Wiśnicki]

On Tue, 04 Jan 2011 20:31:55 +0700, Nguyễn Thái Ngọc Duy wrote:

> gitattr and .gitignore are supposed to use the same rules for matching
> patterns. Unfortunately it's not exactly the same in reality. Mention
> the differences so users won't be surprised, until gitattr gets updates.
> 
> 
> diff --git a/Documentation/gitattributes.txt
> b/Documentation/gitattributes.txt index 5a7f936..cfaf107 100644
> --- a/Documentation/gitattributes.txt +++
> b/Documentation/gitattributes.txt @@ -56,6 +56,7 @@ When more than one
> pattern matches the path, a later line
>  overrides an earlier line.  This overriding is done per attribute.  The
>  rules how the pattern matches paths are the same as in `.gitignore`
>  files; see linkgit:gitignore[5].
> +However patterns that end with a slash is not supported.
>  

I'm afraid that is not all. The rules I've inferred:

  1. No pattern will match directory tree.
  2. It is only possible to match on path components.
  3. If pattern contains slash it is treated as absolute.

Example for file: d1/d2/f1.c

Patterns that match:
  *.c
  d1/d2/*
  /d1/d2/*
  */d2/*
  */*/*

Patterns that do not match but should:
  d2/*
  d2/
  d2
  d1/d2
  /d1/d2

Re: [PATCH] gitattributes.txt: mention exceptions to gitignore rules

[Junio C Hamano]

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

>  2011/1/4 Marcin Wiśnicki <mwisnicki@gmail.com>:
>  > I think that for the time being at least the manual page must change to
>  > reflect reality.
>
>  Looks like changes will be more than just a few lines because path_matches()
>  needs to learn about directories (iow less likely to get fixed right away).
>  So, yes, good idea.

Not really.  I'd rather see a handful of test cases added to t0003 to help
interested parties to see what is broken and what is not.

Quoting from Marcin's other message, assuming that "Patterns" are stored
in either .gitattributes at the top level or .git/info/attributes:

> Example for file: d1/d2/f1.c
> 
> Patterns that match:
>   *.c

No slashes, so it should match anywhere (correct).

>   d1/d2/*

With slashes, so this is anchored at the toplevel of the working tree, and
the path should match (correct).

>   /d1/d2/*

The same as above;, the leading '/' is only to make it explicit that it is
anchored at the level

>   */d2/*

Should match.

>   */*/*

Should match.

> Patterns that do not match but should:
>   d2/*

This shouldn't match unless it appears in d1/.gitattributes.

The presense of '/' makes the pattern anchored to the directory it appear
in, and .git/info/attributes is taken as being at the top level.

>   d2/
>   d2

These shouldn't for the same reason.

>   d1/d2
>   /d1/d2

We somehow don't do leading path match like we do for gitignore, but I do
not think this was intended.  My gut feeling is that these should match.

The thinking back, when we wrote the code, could have been that, unlike
gitignore that maintains only one bit (either "ignored" or "not"),
attributes are richer and giving the same attribute (say "whitespace
checking criteria") to files inside a directory and the containing
directory itself was nonsensical.  But if that was the reason, it is
faulty, as we do not track directories anyway.

Wouldn't it be sufficient to teach attr.c:path_matches() that a pattern
could also match with leading path?  That would automatically cover the
case where a pattern is terminated with a slash, as pattern "d/e/" would
never match path "d/e" but does match "d/e/f"?

Re: [PATCH] gitattributes.txt: mention exceptions to gitignore rules

[Marcin Wiśnicki]

On Tue, 04 Jan 2011 11:17:14 -0800, Junio C Hamano wrote:

>> Patterns that do not match but should:
>>   d2/*
> 
> This shouldn't match unless it appears in d1/.gitattributes.
> 
> The presense of '/' makes the pattern anchored to the directory it
> appear in, and .git/info/attributes is taken as being at the top level.
> 

After more carefully re-reading gitignore(5) I think that now I get it.

I presume that is is not possible to match certain pattern occurring 
*anywhere* in the path.

Would it be possible to extend pattern format to include double-star 
wildcard that matches anything including slashes ?

Like: **/whatever/**

Many tools (in java at least) and libraries support such extension to 
globs. Unfortunately standard fnmatch(3) that's used by git is not one of 
them, but glibc's implementation looks portable and self-contained so it 
could be included and modified.


>>   d2/
>>   d2
> 
> These shouldn't for the same reason.
> 
>>   d1/d2
>>   /d1/d2
> 
> We somehow don't do leading path match like we do for gitignore, but I
> do not think this was intended.  My gut feeling is that these should
> match.
> 
> The thinking back, when we wrote the code, could have been that, unlike
> gitignore that maintains only one bit (either "ignored" or "not"),
> attributes are richer and giving the same attribute (say "whitespace
> checking criteria") to files inside a directory and the containing
> directory itself was nonsensical.  But if that was the reason, it is
> faulty, as we do not track directories anyway.
> 
> Wouldn't it be sufficient to teach attr.c:path_matches() that a pattern
> could also match with leading path?  That would automatically cover the
> case where a pattern is terminated with a slash, as pattern "d/e/" would
> never match path "d/e" but does match "d/e/f"?