submodule: don't access the .gitmodules cache entry after removing it

Commit 5fee995244e introduced the stage_updated_gitmodules() function to
add submodule configuration updates to the index. It assumed that even
after calling remove_cache_entry_at() the same cache entry would still be
valid. This was true in the old days, as cache entries could never be
freed, but that is not so sure in the present as there is ongoing work to
free removed cache entries, which makes this code segfault.

Fix that by calling add_file_to_cache() instead of open coding it. Also
remove the "could not find .gitmodules in index" warning, as that won't
happen in regular use cases (and by then just silently adding it to the
index we do the right thing).

Thanks-to: Karsten Blees <karsten.blees@gmail.com>
Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
add a hashtable implementation that supports O(1) removal

The existing hashtable implementation (in hash.[ch]) uses open addressing
(i.e. resolve hash collisions by distributing entries across the table).
Thus, removal is difficult to implement with less than O(n) complexity.
Resolving collisions of entries with identical hashes (e.g. via chaining)
is left to the client code.

Add a hashtable implementation that supports O(1) removal and is slightly
easier to use due to builtin entry chaining.

Supports all basic operations init, free, get, add, remove and iteration.

Also includes ready-to-use hash functions based on the public domain FNV-1
algorithm (http://www.isthe.com/chongo/tech/comp/fnv).

The per-entry data structure (hashmap_entry) is piggybacked in front of
the client's data structure to save memory. See test-hashmap.c for usage
examples.

The hashtable is resized by a factor of four when 80% full. With these
settings, average memory consumption is about 2/3 of hash.[ch], and
insertion is about twice as fast due to less frequent resizing.

Lookups are also slightly faster, because entries are strictly confined to
their bucket (i.e. no data of other buckets needs to be traversed).

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
buitin/describe.c: use new hash map implementation

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diffcore-rename.c: move code around to prepare for the next patch

No actual code changes, just move hash_filespec up and outdent part of
find_identical_files.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diffcore-rename.c: simplify finding exact renames

The find_exact_renames function currently only uses the hash table for
grouping, i.e.:

1. add sources
2. add destinations
3. iterate all buckets, per bucket:
4. split sources from destinations
5. iterate destinations, per destination:
6. iterate sources to find best match

This can be simplified by utilizing the lookup functionality of the hash
table, i.e.:

1. add sources
2. iterate destinations, per destination:
3. lookup sources matching the current destination
4. iterate sources to find best match

This saves several iterations and file_similarity allocations for the
destinations.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diffcore-rename.c: use new hash map implementation

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
name-hash.c: use new hash map implementation for directories

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
name-hash.c: remove unreferenced directory entries

The new hashmap implementation supports remove, so remove and free
directory entries that are no longer referenced by active cache entries.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
name-hash.c: use new hash map implementation for cache entries

Note: the "ce->next = NULL;" in unpack-trees.c::do_add_entry can safely be
removed, as ce->next (now ce->ent.next) is always properly initialized in
name-hash.c::hash_index_entry.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
name-hash.c: remove cache entries instead of marking them CE_UNHASHED

The new hashmap implementation supports remove, so really remove unused
cache entries from the name hashmap instead of just marking them.

The CE_UNHASHED flag and CE_STATE_MASK are no longer needed.

Keep the CE_HASHED flag to prevent adding entries twice.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
remove old hash.[ch] implementation

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fix 'git update-index --verbose --again' output

'git update-index --verbose' consistently reports paths relative to the
work-tree root. The only exception is the '--again' option, which reports
paths relative to the current working directory.

Change do_reupdate to use non-prefixed paths.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
builtin/update-index.c: cleanup update_one

do_reupdate calls update_one with a cache_entry.name, there's no need for
the extra sanitation / normalization that happens in prefix_path.
cmd_update_index calls update_one with an already prefixed path, no need to
prefix_path twice.

Remove the extra prefix_path from update_one. Also remove the now unused
'prefix' and 'prefix_length' parameters.

As of d089eba "setup: sanitize absolute and funny paths in get_pathspec()",
prefix_path uncoditionally returns a copy, even if the passed in path isn't
changed. Lets unconditionally free() the result.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
read-cache.c: fix memory leaks caused by removed cache entries

When cache_entry structs are removed from index_state.cache, they are not
properly freed. Freeing those entries wasn't possible before because we
couldn't remove them from index_state.name_hash.

Now that we _do_ remove the entries from name_hash, we can also free them.
Add 'free(cache_entry)' to all call sites of name-hash.c::remove_name_hash
in read-cache.c (we could free() directly in remove_name_hash(), but
name-hash.c isn't concerned with cache_entry allocation at all).

Accessing a cache_entry after removing it from the index is now no longer
allowed, as the memory has been freed. The following functions need minor
fixes (typically by copying ce->name before use):
 - builtin/rm.c::cmd_rm
 - builtin/update-index.c::do_reupdate
 - read-cache.c::read_index_unmerged
 - resolve-undo.c::unmerge_index_entry_at

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add test-hashmap to .gitignore

Prevent the "test-hashmap" program from being accidentally tracked
with "git add" or cluttering "git status" output.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Drop unnecessary #includes from test-hashmap

Per Documentation/CodingGuidelines most C files in git start with
a #include of git-compat-util.h or another header file that includes
it, such as cache.h or builtin.h.  This file doesn't need anything
beyond "git-compat-util.h", so use that.

Remove a #include of the system header <stdio.h> since it is already
included by "git-compat-util.h".

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
hashmap.h: Use 'unsigned int' for hash-codes everywhere

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
name-hash: retire unused index_name_exists()

db5360f3f496 (name-hash: refactor polymorphic index_name_exists();
2013-09-17) split index_name_exists() into index_file_exists() and
index_dir_exists() but retained index_name_exists() as a thin wrapper
to avoid disturbing possible in-flight topics. Since this change
landed in 'master' some time ago and there are no in-flight topics
referencing index_name_exists(), retire it.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge commit 'dc85001^2' into HEAD
read-cache: save trailing sha-1

This will be used as signature to know if the index has changed.