Conversion from unsigned char sha1[20] to struct object_id
continues.

* bc/cocci:
  diff: convert prep_temp_blob() to struct object_id
  merge-recursive: convert merge_recursive_generic() to object_id
  merge-recursive: convert leaf functions to use struct object_id
  merge-recursive: convert struct merge_file_info to object_id
  merge-recursive: convert struct stage_data to use object_id
  diff: rename struct diff_filespec's sha1_valid member
  diff: convert struct diff_filespec to struct object_id
  coccinelle: apply object_id Coccinelle transformations
  coccinelle: convert hashcpy() with null_sha1 to hashclr()
  contrib/coccinelle: add basic Coccinelle transforms
  hex: add oid_to_hex_r()

All of the callers of this function use struct object_id, so convert it
to use struct object_id in its arguments and internally.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Now that this struct's sha1 member is called "oid", update the comment
and the sha1_valid member to be called "oid_valid" instead.  The
following Coccinelle semantic patch was used to implement this, followed
by the transformations in object_id.cocci:

@@
struct diff_filespec o;
@@
- o.sha1_valid
+ o.oid_valid

@@
struct diff_filespec *p;
@@
- p->sha1_valid
+ p->oid_valid

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Convert struct diff_filespec's sha1 member to use a struct object_id
called "oid" instead.  The following Coccinelle semantic patch was used
to implement this, followed by the transformations in object_id.cocci:

@@
struct diff_filespec o;
@@
- o.sha1
+ o.oid.hash

@@
struct diff_filespec *p;
@@
- p->sha1
+ p->oid.hash

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

hashcpy with null_sha1 as the source is equivalent to hashclr.  In
addition to being simpler, using hashclr may give the compiler a chance
to optimize better.  Convert instances of hashcpy with the source
argument of null_sha1 to hashclr.

This transformation was implemented using the following semantic patch:

@@
expression E1;
@@
-hashcpy(E1, null_sha1);
+hashclr(E1);

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

"git diff --output=<file> --color=auto" used to show the ANSI color
sequence in the resulting file when the standard output is connected
to a terminal, because --color=auto check always checks the standard
output, not the actual file that receives the output.

We could correct this by using freopen(3) to redirect the standard
output to the specified file, which is in like with how format-patch
used to match the world order, but following the same reasoning as
the earlier "format-patch: explicitly switch off color when writing
to files", let's be more strict by bypassing the "auto" check when
the --output=<file> option is in use.

Strictly speaking, this is a backwards-incompatible change, but
it is highly unlikely that any user would want to see ANSI color
sequences in a file.

The reason this was not caught earlier is most likely that either
--output=<file> is not used, or only when stdout is redirected
anyway.

Users can still give --color=always if they want a colored diff in
the resulting file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

It turns out that the earlier effort to update the heuristics may
want to use a bit more time to mature.  Turn it off by default.

* jk/diff-compact-heuristic:
  diff: disable compaction heuristic for now

http://lkml.kernel.org/g/20160610075043.GA13411@sigill.intra.peff.net
reports that a change to add a new "function" with common ending
with the existing one at the end of the file is shown like this:

    def foo
      do_foo_stuff()

   +  common_ending()
   +end
   +
   +def bar
   +  do_bar_stuff()
   +
      common_ending()
    end

when the new heuristic is in use.  In reality, the change is to add
the blank line before "def bar" and everything below, which is what
the code without the new heuristic shows.

Disable the heuristics by default, and resurrect the documentation
for the option and the configuration variables, while clearly
marking the feature as still experimental.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patch output from "git diff" and friends has been tweaked to be
more readable by using a blank line as a strong hint that the
contents before and after it belong to a logically separate unit.

* jk/diff-compact-heuristic:
  diff: undocument the compaction heuristic knobs for experimentation
  xdiff: implement empty line chunk heuristic
  xdiff: add recs_match helper function

In order to produce the smallest possible diff and combine several diff
hunks together, we implement a heuristic from GNU Diff which moves diff
hunks forward as far as possible when we find common context above and
below a diff hunk. This sometimes produces less readable diffs when
writing C, Shell, or other programming languages, ie:

...
 /*
+ *
+ *
+ */
+
+/*
...

instead of the more readable equivalent of

...
+/*
+ *
+ *
+ */
+
 /*
...

Implement the following heuristic to (optionally) produce the desired
output.

  If there are diff chunks which can be shifted around, shift each hunk
  such that the last common empty line is below the chunk with the rest
  of the context above.

This heuristic appears to resolve the above example and several other
common issues without producing significantly weird results. However, as
with any heuristic it is not really known whether this will always be
more optimal. Thus, it can be disabled via diff.compactionHeuristic.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>