Convert struct cache_entry to use struct object_id by applying the
following semantic patch and the object_id transforms from contrib, plus
the actual change to the struct:

@@
struct cache_entry E1;
@@
- E1.sha1
+ E1.oid.hash

@@
struct cache_entry *E1;
@@
- E1->sha1
+ E1->oid.hash
Signed-off-by: Nbrian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

If a subdirectory contains nothing but i-t-a entries, we generate an
empty tree object and add it to its parent tree. Which is wrong. Such
a subdirectory should not be added.

Note that this has a cascading effect. If subdir 'a/b/c' contains
nothing but i-t-a entries, we ignore it. But then if 'a/b' contains
only (the non-existing) 'a/b/c', then we should ignore 'a/b' while
building 'a' too. And it goes all the way up to top directory.
Noticed-by: NJunio C Hamano <gitster@pobox.com>
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Commit 3cf773e4 (cache-tree: fix writing cache-tree when CE_REMOVE is
present - 2012-12-16) skips i-t-a entries when building trees objects
from the index. Unfortunately it may skip too much.

The code in question checks if an entry is an i-t-a one, then no tree
entry will be written. But it does not take into account that
directories can also be written with the same code. Suppose we have
this in the index.

    a-file
    subdir/file1
    subdir/file2
    subdir/file3
    the-last-file

We write an entry for a-file as normal and move on to subdir/file1,
where we realize the entry name for this level is simply just
"subdir", write down an entry for "subdir" then jump three items ahead
to the-last-file.

That is what happens normally when the first file in subdir is not an
i-t-a entry. If subdir/file1 is an i-t-a, because of the broken
condition in this code, we still think "subdir" is an i-t-a file and
not writing "subdir" down and jump to the-last-file. The result tree
now only has two items: a-file and the-last-file. subdir should be
there too (even though it only records two sub-entries, file2 and
file3).

If the i-t-a entry is subdir/file2 or subdir/file3, this is not a
problem because we jump over them anyway. Which may explain why the
bug is hidden for nearly four years.

Fix it by making sure we only skip i-t-a entries when the entry in
question is actual an index entry, not a directory.
Reported-by: NYuri Kanivetsky <yuri.kanivetsky@gmail.com>
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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

Using FLEX_ARRAY macros reduces the amount of manual
computation size we have to do. It also ensures we don't
overflow size_t, and it makes sure we write the same number
of bytes that we allocated.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Convert all instances of get_object_hash to use an appropriate reference
to the hash member of the oid member of struct object.  This provides no
functional change, as it is essentially a macro substitution.
Signed-off-by: Nbrian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: NJeff King <peff@peff.net>

Convert most instances where the sha1 member of struct object is
dereferenced to use get_object_hash.  Most instances that are passed to
functions that have versions taking struct object_id, such as
get_sha1_hex/get_oid_hex, or instances that can be trivially converted
to use struct object_id instead, are not converted.
Signed-off-by: Nbrian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: NJeff King <peff@peff.net>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

A caller may wish to write a temporary index as a tree. However,
write_cache_as_tree() assumes that the index was read from, and will
write to, the default index file path. Introduce write_index_as_tree()
which removes this limitation by allowing the caller to specify its own
index_state and index file path.
Signed-off-by: NPaul Tan <pyokagan@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The loop in cache-tree's update_one iterates over all the
entries in the index. For each one, we find the cache-tree
subtree which represents our path (creating it if
necessary), and then recurse into update_one again. The
return value we get is the number of index entries that
belonged in that subtree. So for example, with entries:

    a/one
    a/two
    b/one

We start by processing the first entry, "a/one".  We would
find the subtree for "a" and recurse into update_one. That
would then handle "a/one" and "a/two", and return the value
2. The parent function then skips past the 2 handled
entries, and we continue by processing "b/one".

If the recursed-into update_one ever returns 0, then we make
no forward progress in our loop. We would process "a/one"
over and over, infinitely.

This should not happen normally. Any subtree we create must
have at least one path in it (the one that we are
processing!). However, we may also reuse a cache-tree entry
we found in the on-disk index. For the same reason, this
should also never have zero entries. However, certain buggy
versions of libgit2 could produce such bogus cache-tree
records. The libgit2 bug has since been fixed, but it does
not hurt to protect ourselves against bogus input coming
from the on-disk data structures.

Note that this is not a die("BUG") or assert, because it is
not an internal bug, but rather a corrupted on-disk
structure. It's possible that we could even recover from it
(by throwing out the bogus cache-tree entry), but it is not
worth the effort; the important thing is that we report an
error instead of looping infinitely.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Move the interface declaration for the functions in lockfile.c from
cache.h to a new file, lockfile.h. Add #includes where necessary (and
remove some redundant includes of cache.h by files that already
include builtin.h).

Move the documentation of the lock_file state diagram from lockfile.c
to the new header file.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

We punt from repairing the cache-tree during a branch switching if
it involves having to create a new tree object that does not yet
exist in the object store.  "mkdir dir && >dir/file && git add dir"
followed by "git checkout" is one example, when a tree that records
the state of such "dir/" is not in the object store.

However, after discovering that we do not have a tree object that
records the state of "dir/", the caller failed to remember the fact
that it noticed the cache-tree entry it received for "dir/" is
invalidated, it already knows it should not be populating the level
that has "dir/" as its immediate subdirectory, and it is not an
error at all for the sublevel cache-tree entry gave it a bogus
object name it shouldn't even look at.

This led the caller to detect and report a non-existent error.  The
end result was the same and we avoided stuffing a non-existent tree
to the cache-tree, but we shouldn't have issued an alarming error
message to the user.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

When git checkout checks out a branch, create or update the
cache-tree so that subsequent operations are faster.

update_main_cache_tree learned a new flag, WRITE_TREE_REPAIR.  When
WRITE_TREE_REPAIR is set, portions of the cache-tree which do not
correspond to existing tree objects are invalidated (and portions which
do are marked as valid).  No new tree objects are created.
Signed-off-by: NDavid Turner <dturner@twitter.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Avoid scanning strings twice, once with strchr() and then with
strlen(), by using strchrnul().
Helped-by: NJunio C Hamano <gitster@pobox.com>
Signed-off-by: NRohit Mani <rohit.mani@outlook.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The search for the end of the slashes is part of the update of the
path variable for the next iteration as opposed to an update of the
slash variable.  So iterate using path rather than slash.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

There is no need for an early

    return it;

from the loop if slash points at the end of the string, because that
is exactly what will happen when the while condition fails at the
start of the next iteration.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

If *slash == '/', then it is necessarily non-NUL.
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Suggested-by: NJunio Hamano <gitster@pobox.com>
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

slash is initialized to a value that cannot be NULL.  So remove the
guards against slash == NULL later in the loop.
Suggested-by: NDavid Kastrup <dak@gnu.org>
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NDmitry S. Dolzhenko <dmitrys.dolzhenko@yandex.ru>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

I attempted to make index_state->cache[] a "const struct cache_entry **"
to find out how existing entries in index are modified and where. The
question I have is what do we do if we really need to keep track of on-disk
changes in the index. The result is

 - diff-lib.c: setting CE_UPTODATE

 - name-hash.c: setting CE_HASHED

 - preload-index.c, read-cache.c, unpack-trees.c and
   builtin/update-index: obvious

 - entry.c: write_entry() may refresh the checked out entry via
   fill_stat_cache_info(). This causes "non-const struct cache_entry
   *" in builtin/apply.c, builtin/checkout-index.c and
   builtin/checkout.c

 - builtin/ls-files.c: --with-tree changes stagemask and may set
   CE_UPDATE

Of these, write_entry() and its call sites are probably most
interesting because it modifies on-disk info. But this is stat info
and can be retrieved via refresh, at least for porcelain
commands. Other just uses ce_flags for local purposes.

So, keeping track of "dirty" entries is just a matter of setting a
flag in index modification functions exposed by read-cache.c. Except
unpack-trees, the rest of the code base does not do anything funny
behind read-cache's back.

The actual patch is less valueable than the summary above. But if
anyone wants to re-identify the above sites. Applying this patch, then
this:

    diff --git a/cache.h b/cache.h
    index 430d021..1692891 100644
    --- a/cache.h
    +++ b/cache.h
    @@ -267,7 +267,7 @@ static inline unsigned int canon_mode(unsigned int mode)
     #define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)

     struct index_state {
    -	struct cache_entry **cache;
    +	const struct cache_entry **cache;
     	unsigned int version;
     	unsigned int cache_nr, cache_alloc, cache_changed;
     	struct string_list *resolve_undo;

will help quickly identify them without bogus warnings.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Intent-to-add entries used to forbid writing trees so it was not a
problem. After commit 3f6d56de (commit: ignore intent-to-add entries
instead of refusing - 2012-02-07), we can generate trees from an index
with i-t-a entries.

However, the commit forgets to invalidate all paths leading to i-t-a
entries. With fully valid cache-tree (e.g. after commit or
write-tree), diff operations may prefer cache-tree to index and not
see i-t-a entries in the index, because cache-tree does not have them.
Reported-by: NJonathon Mah <me@JonathonMah.com>
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

entry_count is used in update_one() for two purposes:

1. to skip through the number of processed entries in in-memory index
2. to record the number of entries this cache-tree covers on disk

Unfortunately when CE_REMOVE is present these numbers are not the same
because CE_REMOVE entries are automatically removed before writing to
disk but entry_count is not adjusted and still counts CE_REMOVE
entries.

Separate the two use cases into two different variables. #1 is taken
care by the new field count in struct cache_tree_sub and entry_count
is prepared for #2.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The loops in update_one can be increased in two different ways: step
by one for files and by <n> for directories. "for" loop is not
suitable for this as it always steps by one and special handling is
required for directories. Replace them with "while" loops for clarity.
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This code is added in 331fcb59 (git add --intent-to-add: do not let an
empty blob be committed by accident - 2008-11-28) to forbid committing
when i-t-a entries are present. When we allow that, we forgot to
remove this.
Noticed-by: NJunio C Hamano <gitster@pobox.com>
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Originally, "git add -N" was introduced to help users from forgetting to
add new files to the index before they ran "git commit -a".  As an attempt
to help them further so that they do not forget to say "-a", "git commit"
to commit the index as-is was taught to error out, reminding the user that
they may have forgotten to add the final contents of the paths before
running the command.

This turned out to be a false "safety" that is useless.  If the user made
changes to already tracked paths and paths added with "git add -N", and
then ran "git add" to register the final contents of the paths added with
"git add -N", "git commit" will happily create a commit out of the index,
without including the local changes made to the already tracked paths. It
was not a useful "safety" measure to prevent "forgetful" mistakes from
happening.

It turns out that this behaviour is not just a useless false "safety", but
actively hurts use cases of "git add -N" that were discovered later and
have become popular, namely, to tell Git to be aware of these paths added
by "git add -N", so that commands like "git status" and "git diff" would
include them in their output, even though the user is not interested in
including them in the next commit they are going to make.

Fix this ancient UI mistake, and instead make a commit from the index
ignoring the paths added by "git add -N" without adding real contents.

Based on the work by Nguyễn Thái Ngọc Duy, and helped by injection of
sanity from Jonathan Nieder and others on the Git mailing list.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

We'll need to safely create or update the cache-tree data of the_index
from other places.  While at it, give it an argument that lets us
silence the messages produced by unmerged entries (which prevent it
from working).
Signed-off-by: NThomas Rast <trast@student.ethz.ch>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NElijah Newren <newren@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Noticed by valgrind during test t0000.35 “writing this tree without
--missing-ok”.

Even in the cherry-pick foo..bar code path, such an error is the
end of the line.  But maybe some day an interactive porcelain will
want to link to libgit, making this matter.
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Not that anybody should ever get it, but somebody did (probably because
of a flaky filesystem, but whatever).  And each time I see an error
message that I haven't seen before, I decide that next time it will look
better.

So this makes us write more relevant information about exactly which
file ended up having issues with a missing object.  Which will tell
whether it was a tree object, for example, or just a regular file in the
index (and which one).
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

When running "diff-index --cached" after making a change to only a small
portion of the index, there is no point unpacking unchanged subtrees into
the index recursively, only to find that all entries match anyway.  Tweak
unpack_trees() logic that is used to read in the tree object to catch the
case where the tree entry we are looking at matches the index as a whole
by looking at the cache-tree.

As an exercise, after modifying a few paths in the kernel tree, here are
a few numbers on my Athlon 64X2 3800+:

    (without patch, hot cache)
    $ /usr/bin/time git diff --cached --raw
    :100644 100644 b57e1f5... e69de29... M  Makefile
    :100644 000000 8c86b72... 0000000... D  arch/x86/Makefile
    :000000 100644 0000000... e69de29... A  arche
    0.07user 0.02system 0:00.09elapsed 102%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+9407minor)pagefaults 0swaps

    (with patch, hot cache)
    $ /usr/bin/time ../git.git/git-diff --cached --raw
    :100644 100644 b57e1f5... e69de29... M  Makefile
    :100644 000000 8c86b72... 0000000... D  arch/x86/Makefile
    :000000 100644 0000000... e69de29... A  arche
    0.02user 0.00system 0:00.02elapsed 103%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+2446minor)pagefaults 0swaps

Cold cache numbers are very impressive, but it does not matter very much
in practice:

    (without patch, cold cache)
    $ su root sh -c 'echo 3 >/proc/sys/vm/drop_caches'
    $ /usr/bin/time git diff --cached --raw
    :100644 100644 b57e1f5... e69de29... M  Makefile
    :100644 000000 8c86b72... 0000000... D  arch/x86/Makefile
    :000000 100644 0000000... e69de29... A  arche
    0.06user 0.17system 0:10.26elapsed 2%CPU (0avgtext+0avgdata 0maxresident)k
    247032inputs+0outputs (1172major+8237minor)pagefaults 0swaps

    (with patch, cold cache)
    $ su root sh -c 'echo 3 >/proc/sys/vm/drop_caches'
    $ /usr/bin/time ../git.git/git-diff --cached --raw
    :100644 100644 b57e1f5... e69de29... M  Makefile
    :100644 000000 8c86b72... 0000000... D  arch/x86/Makefile
    :000000 100644 0000000... e69de29... A  arche
    0.02user 0.01system 0:01.01elapsed 3%CPU (0avgtext+0avgdata 0maxresident)k
    18440inputs+0outputs (79major+2369minor)pagefaults 0swaps

This of course helps "git status" as well.

    (without patch, hot cache)
    $ /usr/bin/time ../git.git/git-status >/dev/null
    0.17user 0.18system 0:00.35elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+5336outputs (0major+10970minor)pagefaults 0swaps

    (with patch, hot cache)
    $ /usr/bin/time ../git.git/git-status >/dev/null
    0.10user 0.16system 0:00.27elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+5336outputs (0major+3921minor)pagefaults 0swaps
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Earlier cache_tree_find() needs to be called with a valid cache_tree,
but repeated look-up may find an invalid or missing cache_tree in between.
Help simplify the callers by returning NULL to mean "nothing appropriate
found" when the input is NULL.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This allows you to discard the cache-tree information before writing the
tree out of the index (i.e. it always recomputes the tree object names for
all the subtrees).

This is only useful as a debug option, so I did not bother documenting it.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The interface to build cache-tree belongs there.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>