This adds "attribute macros" (for lack of better name). So far,
we have low-level attributes such as crlf and diff, which are
defined in operational terms --- setting or unsetting them on a
particular path directly affects what is done to the path. For
example, in order to decline diffs or crlf conversions on a
binary blob, no diffs on PostScript files, and treat all other
files normally, you would have something like these:
* diff crlf
*.ps !diff
proprietary.o !diff !crlf
That is fine as the operation goes, but gets unwieldy rather
rapidly, when we start adding more low-level attributes that are
defined in operational terms. A near-term example of such an
attribute would be 'merge-3way' which would control if git
should attempt the usual 3-way file-level merge internally, or
leave merging to a specialized external program of user's
choice. When it is added, we do _not_ want to force the users
to update the above to:
* diff crlf merge-3way
*.ps !diff
proprietary.o !diff !crlf !merge-3way
The way this patch solves this issue is to realize that the
attributes the user is assigning to paths are not defined in
terms of operations but in terms of what they are.
All of the three low-level attributes usually make sense for
most of the files that sane SCM users have git operate on (these
files are typically called "text'). Only a few cases, such as
binary blob, need exception to decline the "usual treatment
given to text files" -- and people mark them as "binary".
So this allows the $GIT_DIR/info/alternates and .gitattributes
at the toplevel of the project to also specify attributes that
assigns other attributes. The syntax is '[attr]' followed by an
attribute name followed by a list of attribute names:
[attr] binary !diff !crlf !merge-3way
When "binary" attribute is set to a path, if the path has not
got diff/crlf/merge-3way attribute set or unset by other rules,
this rule unsets the three low-level attributes.
It is expected that the user level .gitattributes will be
expressed mostly in terms of attributes based on what the files
are, and the above sample would become like this:
(built-in attribute configuration)
[attr] binary !diff !crlf !merge-3way
* diff crlf merge-3way
(project specific .gitattributes)
proprietary.o binary
(user preference $GIT_DIR/info/attributes)
*.ps !diff
There are a few caveats.
* As described above, you can define these macros only in
$GIT_DIR/info/attributes and toplevel .gitattributes.
* There is no attempt to detect circular definition of macro
attributes, and definitions are evaluated from bottom to top
as usual to fill in other attributes that have not yet got
values. The following would work as expected:
[attr] text diff crlf
[attr] ps text !diff
*.ps ps
while this would most likely not (I haven't tried):
[attr] ps text !diff
[attr] text diff crlf
*.ps ps
* When a macro says "[attr] A B !C", saying that a path does
not have attribute A does not let you tell anything about
attributes B or C. That is, given this:
[attr] text diff crlf
[attr] ps text !diff
*.txt !ps
path hello.txt, which would match "*.txt" pattern, would have
"ps" attribute set to zero, but that does not make text
attribute of hello.txt set to false (nor diff attribute set to
true).
Signed-off-by: Junio C Hamano <junkio@cox.net>
This makes paths that explicitly unset 'diff' attribute not to
produce "textual" diffs from 'git-diff' family.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This defines the semantics of 'crlf' attribute as an example.
When a path has this attribute unset (i.e. '!crlf'), autocrlf
line-end conversion is not applied.
Eventually we would want to let users to build a pipeline of
processing to munge blob data to filesystem format (and in the
other direction) based on combination of attributes, and at that
point the mechanism in convert_to_{git,working_tree}() that
looks at 'crlf' attribute needs to be enhanced. Perhaps the
existing 'crlf' would become the first step in the input chain,
and the last step in the output chain.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds the basic infrastructure to assign attributes to
paths, in a way similar to what the exclusion mechanism does
based on $GIT_DIR/info/exclude and .gitignore files.
An attribute is just a simple string that does not contain any
whitespace. They can be specified in $GIT_DIR/info/attributes
file, and .gitattributes file in each directory.
Each line in these files defines a pattern matching rule.
Similar to the exclusion mechanism, a later match overrides an
earlier match in the same file, and entries from .gitattributes
file in the same directory takes precedence over the ones from
parent directories. Lines in $GIT_DIR/info/attributes file are
used as the lowest precedence default rules.
A line is either a comment (an empty line, or a line that begins
with a '#'), or a rule, which is a whitespace separated list of
tokens. The first token on the line is a shell glob pattern.
The rest are names of attributes, each of which can optionally
be prefixed with '!'. Such a line means "if a path matches this
glob, this attribute is set (or unset -- if the attribute name
is prefixed with '!'). For glob matching, the same "if the
pattern does not have a slash in it, the basename of the path is
matched with fnmatch(3) against the pattern, otherwise, the path
is matched with the pattern with FNM_PATHNAME" rule as the
exclusion mechanism is used.
This does not define what an attribute means. Tying an
attribute to various effects it has on git operation for paths
that have it will be specified separately.
Signed-off-by: Junio C Hamano <junkio@cox.net>
