When an object is made unreachable by Git, any notes that annotate that object
are not automagically made unreachable, since all notes are always trivially
reachable from a notes ref. In order to remove notes for non-existing objects,
we therefore need to add functionality for traversing the notes tree and
explicitly removing references to notes that annotate non-reachable objects.
Thus the notes objects themselves also become unreachable, and are removed
by a later garbage collect.
prune_notes() performs this traversal (by using for_each_note() internally),
and removes the notes in question from the notes tree.
Note that the effect of prune_notes() is not persistent unless a subsequent
call to write_notes_tree() is made.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The note tree structure allows for non-note entries to coexist with note
entries in a notes tree. Although we certainly expect there to be very
few non-notes in a notes tree, we should still support them to a certain
degree.
This patch teaches the notes code to preserve non-notes when updating the
notes tree with write_notes_tree(). Non-notes are not affected by fanout
restructuring.
For non-notes to be handled correctly, we can no longer allow subtree
entries that do not match the fanout structure produced by the notes code
itself. This means that fanouts like 4/36, 6/34, 8/32, 4/4/32, etc. are
no longer recognized as note subtrees; only 2-based fanouts are allowed
(2/38, 2/2/36, 2/2/2/34, etc.). Since the notes code has never at any point
_produced_ non-2-based fanouts, it is highly unlikely that this change will
cause problems for anyone.
The patch also adds some tests verifying the correct handling of non-notes
in a notes tree.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When adding a note to an object that already has an existing note, the
current solution is to concatenate the contents of the two notes. However,
the caller may instead wish to _overwrite_ the existing note with the new
note, or maybe even _ignore_ the new note, and keep the existing one. There
might also be other ways of combining notes that are only known to the
caller.
Therefore, instead of unconditionally concatenating notes, we let the caller
specify how to combine notes, by passing in a pointer to a function for
combining notes. The caller may choose to implement its own function for
notes combining, but normally one of the following three conveniently
supplied notes combination functions will be sufficient:
- combine_notes_concatenate() combines the two notes by appending the
contents of the new note to the contents of the existing note.
- combine_notes_overwrite() replaces the existing note with the new note.
- combine_notes_ignore() keeps the existing note, and ignores the new note.
A combine_notes function can be passed to init_notes() to choose a default
combine_notes function for that notes tree. If NULL is given, the notes tree
falls back to combine_notes_concatenate() as the ultimate default.
A combine_notes function can also be passed directly to add_note(), to
control the notes combining behaviour for a note addition in particular.
If NULL is passed, the combine_notes function registered for the given
notes tree is used.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The new struct notes_tree encapsulates access to a specific notes tree.
It is provided to allow callers to make use of several different notes trees
simultaneously.
A struct notes_tree * parameter is added to every function in the notes API.
In all cases, NULL can be passed, in which case the fallback "default" notes
tree (default_notes_tree) is used.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Uses for_each_note() to traverse the notes tree, and produces tree
objects on the fly representing the "on-disk" version of the notes
tree with appropriate fanout.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This includes a first attempt at creating an optimal fanout scheme (which
is calculated on-the-fly, while traversing).
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Created by a simple cleanup and rename of lookup_notes().
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This includes adding internal functions for maintaining a healthy notes tree
structure after removing individual notes.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Created by a simple refactoring of initialize_notes().
Also add a new 'flags' parameter, which is a bitwise combination of notes
initialization flags. For now, there is only one flag - NOTES_INIT_EMPTY -
which indicates that the notes tree should not auto-load the contents of
the given (or default) notes ref, but rather should leave the notes tree
initialized to an empty state. This will become useful in the future when
manipulating the notes tree through the notes API.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There is really no reason why only commit objects can be annotated. By
changing the struct commit parameter to get_commit_notes() into a sha1 we
gain the ability to annotate any object type. To reflect this in the function
naming as well, we rename get_commit_notes() to format_note().
This patch also fixes comments and variable names throughout notes.c as a
consequence of the removal of the unnecessary 'commit' restriction.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When loading a notes tree, the code primarily looks for SHA1-like paths
whose total length (discounting directory separators) are 40 chars
(interpreted as valid note entries) or less (interpreted as subtree
entries that may in turn contain note entries when unpacked).
However, there is an additional condition that must hold for valid
subtree entries: They must be _tree_ objects (duh).
This patch adds an appropriate test for this condition, thereby fixing
the crash that occured when passing a non-tree object to the tree-walk
API.
The patch also adds another selftest verifying correct behaviour of
non-notes in note trees.
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Currently, having multiple notes referring to the same commit from various
locations in the notes tree is strongly discouraged, since only one of those
notes will be parsed and shown.
This patch teaches the notes code to _concatenate_ multiple notes that
annotate the same commit. Notes are concatenated by creating a new blob
object containing the concatenation of the notes in question, and
replacing them with the concatenated note in the internal notes tree
structure.
Getting the concatenation right requires being more proactive in unpacking
subtree entries in the internal notes tree structure, so that we don't return
a note prematurely (i.e. before having found all other notes that annotate
the same object). As such, this patch may incur a small performance penalty.
Suggested-by: Sam Vilain <sam@vilain.net>
Re-suggested-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The semantics used when parsing notes trees (with regards to fanout subtrees)
follow Dscho's proposal fairly closely:
- No concatenation/merging of notes is performed. If there are several notes
objects referencing a given commit, only one of those objects are used.
- If a notes object for a given commit is present in the "root" notes tree,
no subtrees are consulted; the object in the root tree is used directly.
- If there are more than one subtree that prefix-matches the given commit,
only the subtree with the longest matching prefix is consulted. This
means that if the given commit is e.g. "deadbeef", and the notes tree have
subtrees "de" and "dead", then the following paths in the notes tree are
searched: "deadbeef", "dead/beef". Note that "de/adbeef" is NOT searched.
- Fanout directories (subtrees) must references a whole number of bytes
from the SHA1 sum they subdivide. E.g. subtrees "dead" and "de" are
acceptable; "d" and "dea" are not.
- Multiple levels of fanout are allowed. All the above rules apply
recursively. E.g. "de/adbeef" is preferred over "de/adbe/ef", etc.
This patch changes the in-memory datastructure for holding parsed notes:
Instead of holding all note (and subtree) entries in a hash table, a
simple 16-tree structure is used instead. The tree structure consists of
16-arrays as internal nodes, and note/subtree entries as leaf nodes. The
tree is traversed by indexing subsequent nibbles of the search key until
a leaf node is encountered. If a subtree entry is encountered while
searching for a note, the subtree is unpacked into the 16-tree structure,
and the search continues into that subtree.
The new algorithm performs significantly better in the cases where only
a fraction of the notes need to be looked up (this is assumed to be the
common case for notes lookup). The new code even performs marginally
better in the worst case (where _all_ the notes are looked up).
In addition to this, comes the massive performance win associated with
organizing the notes tree according to some fanout scheme. Even a simple
2/38 fanout scheme is dramatically quicker to traverse (going from tens of
seconds to sub-second runtimes).
As for memory usage, the new code is marginally better than the old code in
the worst case, but in the case of looking up only some notes from a notes
tree with proper fanout, the new code uses only a small fraction of the
memory needed to hold the entire notes tree.
However, there is one casualty of this patch. The old notes lookup code was
able to parse notes that were associated with non-SHA1s (e.g. refs). The new
code requires the referenced object to be named by a SHA1 sum. Still, this
is not considered a major setback, since the notes infrastructure was not
originally intended to annotate objects outside the Git object database.
Cc: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There's no need to be rude to memory-concious callers...
This patch has been improved by the following contributions:
- Junio C Hamano: avoid old-style declaration
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This patch adds the following flags to get_commit_notes() for adjusting the
format of the produced note string:
- NOTES_SHOW_HEADER: Print "Notes:" line before the notes contents
- NOTES_INDENT: Indent notes contents by 4 spaces
Suggested-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
To avoid looking up each and every commit in the notes ref's tree
object, which is very expensive, speed things up by slurping the tree
object's contents into a hash_map.
The idea for the hashmap singleton is from David Reiss, initial
benchmarking by Jeff King.
Note: the implementation allows for arbitrary entries in the notes
tree object, ignoring those that do not reference a valid object. This
allows you to annotate arbitrary branches, or objects.
This patch has been improved by the following contributions:
- Junio C Hamano: fixed an obvious error in initialize_hash_map()
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit notes are blobs which are shown together with the commit
message. These blobs are taken from the notes ref, which you can
configure by the config variable core.notesRef, which in turn can
be overridden by the environment variable GIT_NOTES_REF.
The notes ref is a branch which contains "files" whose names are
the names of the corresponding commits (i.e. the SHA-1).
The rationale for putting this information into a ref is this: we
want to be able to fetch and possibly union-merge the notes,
maybe even look at the date when a note was introduced, and we
want to store them efficiently together with the other objects.
This patch has been improved by the following contributions:
- Thomas Rast: fix core.notesRef documentation
- Tor Arne Vestbø: fix printing of multi-line notes
- Alex Riesen: Using char array instead of char pointer costs less BSS
- Johan Herland: Plug leak when msg is good, but msglen or type causes return
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Tor Arne Vestbø <tavestbo@trolltech.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
get_commit_notes(): Plug memory leak when 'if' triggers, but not because of read_sha1_file() failure
The line length was read from the same position every time,
causing mangled output when printing notes with multiple lines.
Also, adding new-line manually for each line ensures that we
get a new-line between commits, matching git-log for commits
without notes.
Signed-off-by: Tor Arne Vestbø <tavestbo@trolltech.com>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
To avoid looking up each and every commit in the notes ref's tree
object, which is very expensive, speed things up by slurping the tree
object's contents into a hash_map.
The idea fo the hashmap singleton is from David Reiss, initial
benchmarking by Jeff King.
Note: the implementation allows for arbitrary entries in the notes
tree object, ignoring those that do not reference a valid object. This
allows you to annotate arbitrary branches, or objects.
[jc: fixed an obvious error in initialize_hash_map()]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit notes are blobs which are shown together with the commit
message. These blobs are taken from the notes ref, which you can
configure by the config variable core.notesRef, which in turn can
be overridden by the environment variable GIT_NOTES_REF.
The notes ref is a branch which contains "files" whose names are
the names of the corresponding commits (i.e. the SHA-1).
The rationale for putting this information into a ref is this: we
want to be able to fetch and possibly union-merge the notes,
maybe even look at the date when a note was introduced, and we
want to store them efficiently together with the other objects.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
