t4056: add new tests for "git diff -O"

Adapted from $gmane/236427 by Anders Waldenborg, "diff: Add
diff.orderfile configuration variable".

Signed-off-by: Anders Waldenborg <anders@0x63.nu>
Signed-off-by: Samuel Bronson <naesten@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff: let "git diff -O" read orderfile from any file and fail properly

The -O flag really shouldn't silently fail to do anything when given
a path that it can't read from.

However, it should be able to read from un-mmappable files, such as:

 * pipes/fifos

 * /dev/null:  It's a character device (at least on Linux)

 * ANY empty file:

   Quoting Linux mmap(2), "SUSv3 specifies that mmap() should fail if
   length is 0.  However, in kernels before 2.6.12, mmap() succeeded in
   this case: no mapping was created and the call returned addr.  Since
   kernel 2.6.12, mmap() fails with the error EINVAL for this case."

We especially want "-O/dev/null" to work, since we will be documenting
it as the way to cancel "diff.orderfile" when we add that.

(Note: "-O/dev/null" did have the right effect, since the existing error
handling essentially worked out to "silently ignore the orderfile".  But
this was probably more coincidence than anything else.)

So, lets toss all of that logic to get the file mmapped and just use
strbuf_read_file() instead, which gives us decent error handling
practically for free.

Signed-off-by: Samuel Bronson <naesten@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff: add diff.orderfile configuration variable

diff.orderfile acts as a default for the -O command line option.

[sb: split up aw's original patch; rework tests and docs, treat option
as pathname]

Signed-off-by: Anders Waldenborg <anders@0x63.nu>
Signed-off-by: Samuel Bronson <naesten@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
log: properly handle decorations with chained tags

git log did not correctly handle decorations when a tag object referenced
another tag object that was no longer a ref, such as when the second tag was
deleted.  The commit would not be decorated correctly because parse_object had
not been called on the second tag and therefore its tagged field had not been
filled in, resulting in none of the tags being associated with the relevant
commit.

Call parse_object to fill in this field if it is absent so that the chain of
tags can be dereferenced and the commit can be properly decorated.  Include
tests as well to prevent future regressions.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'kb/fast-hashmap' (early part) into jch

* 'kb/fast-hashmap' (early part):
  Drop unnecessary #includes from test-hashmap
  Add test-hashmap to .gitignore
  read-cache.c: fix memory leaks caused by removed cache entries
  builtin/update-index.c: cleanup update_one
  fix 'git update-index --verbose --again' output
  remove old hash.[ch] implementation
  name-hash.c: remove cache entries instead of marking them CE_UNHASHED
  name-hash.c: use new hash map implementation for cache entries
  name-hash.c: remove unreferenced directory entries
  name-hash.c: use new hash map implementation for directories
  diffcore-rename.c: use new hash map implementation
  diffcore-rename.c: simplify finding exact renames
  diffcore-rename.c: move code around to prepare for the next patch
  buitin/describe.c: use new hash map implementation
  add a hashtable implementation that supports O(1) removal
  submodule: don't access the .gitmodules cache entry after removing it
Merge branch 'nd/negative-pathspec' into jch

Introduce "negative pathspec" magic, to allow "git log -- . ':!dir'" to
tell us "I am interested in everything but 'dir' directory".

* nd/negative-pathspec:
  pathspec.c: support adding prefix magic to a pathspec with mnemonic magic
  Support pathspec magic :(exclude) and its short form :!
  glossary-content.txt: rephrase magic signature part
Merge branch 'cc/replace-object-info' into jch

read_sha1_file() that is the workhorse to read the contents given
an object name honoured object replacements, but there is no
corresponding mechanism to sha1_object_info() that is used to
obtain the metainfo (e.g. type & size) about the object, leading
callers to weird inconsistencies.

Has this been reviewed sufficiently?

* cc/replace-object-info:
  Documentation/git-replace: describe --format option
  builtin/replace: unset read_replace_refs
  t6050: add tests for listing with --format
  builtin/replace: teach listing using short, medium or full formats
  sha1_file: perform object replacement in sha1_object_info_extended()
  t6050: show that git cat-file --batch fails with replace objects
  sha1_object_info_extended(): add an "unsigned flags" parameter
  sha1_file.c: add lookup_replace_object_extended() to pass flags
  replace_object: don't check read_replace_refs twice
  rename READ_SHA1_FILE_REPLACE flag to LOOKUP_REPLACE_OBJECT
### 2.0
Merge branch 'jc/push-2.0-default-to-simple' into jch

* jc/push-2.0-default-to-simple:
  push: switch default from "matching" to "simple"

# Conflicts:
# 	Documentation/config.txt
# 	Documentation/git-push.txt
# 	builtin/push.c
Merge branch 'jn/add-2.0-u-A-sans-pathspec' into jch

* jn/add-2.0-u-A-sans-pathspec:
  git add: -u/-A now affects the entire working tree

# Conflicts:
# 	builtin/add.c
Merge branch 'jc/add-2.0-ignore-removal' into jch

Updated endgame for "git add <pathspec>" that defaults to "--all"
aka "--no-ignore-removal".

* jc/add-2.0-ignore-removal:
  git add <pathspec>... defaults to "-A"

# Conflicts:
# 	builtin/add.c
Merge branch 'jc/core-checkstat-2.0' into jch

* jc/core-checkstat-2.0:
  core.statinfo: remove as promised in Git 2.0
Merge branch 'gj/push-more-verbose-advice' into jch

Explain 'simple' and 'matching' in "git push" advice message; the
topmost patch is a rebase of jc/push-2.0-default-to-simple on top
of it.

* gj/push-more-verbose-advice:
  push: switch default from "matching" to "simple"
Merge branch 'jc/hold-diff-remove-q-synonym-for-no-deletion' into jch

* jc/hold-diff-remove-q-synonym-for-no-deletion:
  diff: remove "diff-files -q" in a version of Git in a distant future

# Conflicts:
# 	diff-no-index.c
# 	diff.c
### match next
Merge branch 'ap/path-max' into jch

* ap/path-max:
  Prevent buffer overflows when path is too long
Merge branch 'jn/git-gui-chmod+x' into jch

* jn/git-gui-chmod+x:
  git-gui: chmod +x po2msg, windows/git-gui.sh
Merge branch 'jn/gitk-chmod+x' into jch

* jn/gitk-chmod+x:
  gitk: chmod +x po2msg
Merge branch 'cc/starts-n-ends-with-endgame' into jch

Endgame for the cc/starts-n-ends-with topic; this needs to be
evil-merged with other topics that introduce new uses of
prefix/suffix-cmp functions.

* cc/starts-n-ends-with-endgame:
  strbuf: remove prefixcmp() and suffixcmp()
Merge branch 'nd/shallow-clone' into jch

Fetching from a shallow-cloned repository used to be forbidden,
primarily because the codepaths involved were not carefully vetted
and we did not bother supporting such usage. This attempts to allow
object transfer out of a shallow-cloned repository in a controlled
way (i.e. the receiver become a shallow repository with truncated
history).

* nd/shallow-clone: (28 commits)
  git-clone.txt: remove shallow clone limitations
  prune: clean .git/shallow after pruning objects
  clone: use git protocol for cloning shallow repo locally
  send-pack: support pushing from a shallow clone via http
  receive-pack: support pushing to a shallow clone via http
  smart-http: support shallow fetch/clone
  remote-curl: pass ref SHA-1 to fetch-pack as well
  send-pack: support pushing to a shallow clone
  receive-pack: allow pushes that update .git/shallow
  connected.c: add new variant that runs with --shallow-file
  add GIT_SHALLOW_FILE to propagate --shallow-file to subprocesses
  receive/send-pack: support pushing from a shallow clone
  receive-pack: reorder some code in unpack()
  fetch: add --update-shallow to accept refs that update .git/shallow
  upload-pack: make sure deepening preserves shallow roots
  fetch: support fetching from a shallow repository
  clone: support remote shallow repository
  fetch-pack.h: one statement per bitfield declaration
  fetch-pack.c: move shallow update code out of fetch_pack()
  shallow.c: steps 6 and 7 to select new commits for .git/shallow
  ...