To improve runtime performance, caching the WorkingTreeOptions inside
of the Config object using the Config.SectionParser API allows
the WorkingTreeOptions to be accessed more efficiently whenever a
FileTreeIterator is constructed for the Repository.

Instead of passing the filemode handling option into isModified(),
the WorkingTreeIterator should always honor whatever setting has
been configured in this repository, as defined by its own copy of
the WorkingTreeOptions.  This simplifies all of the callers as they
no longer need to lookup core.filemode on their own.

A few locations were changed from always using a hardcoded "true"
on the file mode to passing what is actually configured in the
repository.  This is a behavior change, but corrects what should be
considered to be bugs as the core.filemode variable wasn't always
being used.

Change-Id: Idb176736fa0dc97af372f1d652a94ecc72fb457c
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

The core.autocrlf variable can take on three values: false, true,
and input.  Parsing it as a boolean is wrong, we instead need to
parse a tri-state enumeration.

Add support for parsing and setting enum values from Java from and
to the text based configuration file, and use that to handle the
autocrlf variable.

Bug: 301775
Change-Id: I81b9e33087a33d2ef2eac89ba93b9e83b7ecc223
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

WorkingTreeIterator now optionally performs CRLF to LF conversion for
text files.  A basic framework is left in place to support enabling
(or disabling) this feature based on gitattributes, and also to
support the more generic smudge/clean filter system.  As there is
no gitattribute support yet in JGit this is left unimplemented,
but the mightNeedCleaning(), isBinary() and filterClean() methods
will provide reasonable places to plug that into in the future.

[sp: All bugs inside of WorkingTreeIterator are my fault, I wrote
     most of it while cherry-picking this patch and building it on
     top of Marc's original work.]

CQ: 4419
Bug: 301775
Change-Id: I0ca35cfbfe3f503729cbfc1d5034ad4abcd1097e
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

We don't actually need a Repository object here, just an ObjectReader
that can load content for us.  So change the API to depend on that.

However, this breaks the asCommit and asTag legacy translation methods
on RevCommit and RevTag, so we still have to keep the Repository
inside of RevWalk for those two types.  Hopefully we can drop those in
the future, and then drop the Repository off the RevWalk.

Change-Id: Iba983e48b663790061c43ae9ffbb77dfe6f4818e
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Per CQ 3448 this is the initial contribution of the JGit project
to eclipse.org.  It is derived from the historical JGit repository
at commit 3a2dd9921c.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>