Re: [PATCH v2 0/6] Extensions of core.ignorecase=true support

Referring back to my earlier comment to this patch series, which was
proposed on August 17, while I tend to agree to the changes that help
listing- operations, those changes that fold case concern me. Let me
explain...

You may find there is a strong contingent of people that would approve
of, and would want to use, case insensitivity for gitignore and ls,
for example; but by tying the same single property (core.ignorecase)
to the case folding behaviors some people would avoid the feature all
together, which would be unfortunate, when they otherwise could
benefit from at least one part of the new behavior.

There were several key things that went wrong in early git
development, this and the eol support were two casualties. The eol
support, as you recall, deprecated the old property in favor of a
couple new superior ones. I would recommend that the same thing be
done here, deprecate the old ignorecase property by introducing two
better ones.

So I could we please separate the behaviors that change intent
(folding) from the behaviors that merely alter how things are
displayed (listing) by splitting this into two separate properties?
For example,

core.casepreserving=true|false
core.caseinsensitive=true|false

The former property would control folding, the latter property would
apply to listing and pattern matching. Then people could opt out of
the folding behaviors (add, import), while continuing to adopt listing
and pattern matching (status, ls, ignore).

Again, deprecate core.ignorecase by making it default to {false,false}
for the new properties if unspecified, which would also be the default
if all three of the properties are unspecified. If ignorecase is
specified to be true, then default to {false, true}, respectively.

Would this be possible?

On Sun, Oct 3, 2010 at 12:32 AM, Joshua Jensen
[off-list ref] wrote:

The second version of this patch series fixes the problematic case
insensitive fnmatch call in patch 1 that relied on an apparently GNU-only
extension.  Instead, the pattern and string are lowercased into
temporary buffers, and the standard fnmatch is called without relying
on the GNU extension.

Patches 2-6 received no modifications.

The original cover for the patch series follows as posted by Johannes Sixt:

The following patch series extends the core.ignorecase=true support to
handle case insensitive comparisons for the .gitignore file, git status,
and git ls-files.  git add and git fast-import will fold the case of the
file being added, matching that of an already added directory entry.  Case
folding is also applied to git fast-import for renames, copies, and deletes.

The most notable benefit, IMO, is that the case of directories in the
worktree does not matter if, and only if, the directory exists already in
the index with some different case variant.  This helps applications on
Windows that change the case even of directories in unpredictable ways.
Joshua mentioned Perforce as the primary example.

Concerning the implementation, Joshua explained when he initially submitted
the series to the msysgit mailing list:

 git status and add both use an update made to name-hash.c where
 directories, specifically names with a trailing slash, can be looked up
 in a case insensitive manner. After trying a myriad of solutions, this
 seemed to be the cleanest. Does anyone see a problem with embedding the
 directory names in the same hash as the file names? I couldn't find one,
 especially since I append a slash to each directory name.

 The git add path case folding functionality is a somewhat radical
 departure from what Git does now. It is described in detail in patch 5.
 Does anyone have any concerns?

I support the idea of this patch, and I can confirm that it works: I've
used this series in production both with core.ignorecase set to true and
to false, and in the former case, with directories and files with case
different from the index.

Joshua Jensen (6):
     Add string comparison functions that respect the ignore_case variable.
     Case insensitivity support for .gitignore via core.ignorecase
     Add case insensitivity support for directories when using git status
     Add case insensitivity support when using git ls-files
     Support case folding for git add when core.ignorecase=true
     Support case folding in git fast-import when core.ignorecase=true


 dir.c         |  152 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
 dir.h         |    4 ++
 fast-import.c |    7 ++-
 name-hash.c   |   72 +++++++++++++++++++++++++++
 read-cache.c  |   23 +++++++++
 5 files changed, 235 insertions(+), 23 deletions(-)


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