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Author SHA1 Message Date

Author	SHA1	Message	Date
Junio C Hamano	730f72840c	unpack-trees.c: look ahead in the index This makes the traversal of index be in sync with the tree traversal. When unpack_callback() is fed a set of tree entries from trees, it inspects the name of the entry and checks if the an index entry with the same name could be hiding behind the current index entry, and (1) if the name appears in the index as a leaf node, it is also fed to the n_way_merge() callback function; (2) if the name is a directory in the index, i.e. there are entries in that are underneath it, then nothing is fed to the n_way_merge() callback function; (3) otherwise, if the name comes before the first eligible entry in the index, the index entry is first unpacked alone. When traverse_trees_recursive() descends into a subdirectory, the cache_bottom pointer is moved to walk index entries within that directory. All of these are omitted for diff-index, which does not even want to be fed an index entry and a tree entry with D/F conflicts. This fixes 3-way read-tree and exposes a bug in other parts of the system in t6035, test #5. The test prepares these three trees: O = HEAD^ 100644 blob `e69de29bb2` a/b-2/c/d 100644 blob `e69de29bb2` a/b/c/d 100644 blob `e69de29bb2` a/x A = HEAD 100644 blob `e69de29bb2` a/b-2/c/d 100644 blob `e69de29bb2` a/b/c/d 100644 blob 587be6b4c3f93f93c489c0111bba5596147a26cb a/x B = master 120000 blob a36b77384451ea1de7bd340ffca868249626bc52 a/b 100644 blob `e69de29bb2` a/b-2/c/d 100644 blob `e69de29bb2` a/x With a clean index that matches HEAD, running git read-tree -m -u --aggressive $O $A $B now yields 120000 a36b77384451ea1de7bd340ffca868249626bc52 3 a/b 100644 `e69de29bb2` 0 a/b-2/c/d 100644 `e69de29bb2` 1 a/b/c/d 100644 `e69de29bb2` 2 a/b/c/d 100644 587be6b4c3f93f93c489c0111bba5596147a26cb 0 a/x which is correct. "master" created "a/b" symlink that did not exist, and removed "a/b/c/d" while HEAD did not do touch either path. Before this series, read-tree did not notice the situation and resolved addition of "a/b" and removal of "a/b/c/d" independently. If A = HEAD had another path "a/b/c/e" added, this merge should conflict but instead it silently resolved "a/b" and then immediately overwrote it to add "a/b/c/e", which was quite bogus. Tests in t1012 start to work with this. Signed-off-by: Junio C Hamano <gitster@pobox.com>	15 years ago
Junio C Hamano	1ee26571e9	traverse_trees(): handle D/F conflict case sanely traverse_trees() is supposed to call its callback with all the matching entries from the given trees. The current algorithm keeps a pointer to each of the tree being traversed, and feeds the entry with the earliest name to the callback. This breaks down if the trees being traversed looks like this: A B t-1 t t-2 u t/a v When we are currently looking at an entry "t-1" in tree A, and tree B has returned "t", feeding "t" from the B and not feeding anything from A, only because "t-1" sorts later than "t", will miss an entry for a subtree "t" behind the current entry in tree A. This introduces extended_entry_extract() helper function that gives what name is expected from the tree, and implements a mechanism to look-ahead in the tree object using it, to make sure such a case is handled sanely. Traversal in tree A in the above example will first return "t" to match that of B, and then the next request for an entry to A then returns "t-1". This roughly corresponds to what Linus's "prepare for one-entry lookahead" wanted to do, but because this does implement look ahead, t6035 and one more test in t1012 reveal that the approach would not work without adjusting the side that walks the index in unpack_trees() as well. Signed-off-by: Junio C Hamano <gitster@pobox.com>	15 years ago
Junio C Hamano	934f930b31	more D/F conflict tests Before starting to muck with this code, let's expose the current breakages that we intend to fix. Signed-off-by: Junio C Hamano <gitster@pobox.com>	15 years ago

Junio C Hamano

730f72840c

unpack-trees.c: look ahead in the index

This makes the traversal of index be in sync with the tree traversal.
When unpack_callback() is fed a set of tree entries from trees, it
inspects the name of the entry and checks if the an index entry with
the same name could be hiding behind the current index entry, and

 (1) if the name appears in the index as a leaf node, it is also
     fed to the n_way_merge() callback function;

 (2) if the name is a directory in the index, i.e. there are entries in
     that are underneath it, then nothing is fed to the n_way_merge()
     callback function;

 (3) otherwise, if the name comes before the first eligible entry in the
     index, the index entry is first unpacked alone.

When traverse_trees_recursive() descends into a subdirectory, the
cache_bottom pointer is moved to walk index entries within that directory.

All of these are omitted for diff-index, which does not even want to be
fed an index entry and a tree entry with D/F conflicts.

This fixes 3-way read-tree and exposes a bug in other parts of the system
in t6035, test #5.  The test prepares these three trees:

 O = HEAD^
    100644 blob e69de29bb2    a/b-2/c/d
    100644 blob e69de29bb2    a/b/c/d
    100644 blob e69de29bb2    a/x

 A = HEAD
    100644 blob e69de29bb2    a/b-2/c/d
    100644 blob e69de29bb2    a/b/c/d
    100644 blob 587be6b4c3f93f93c489c0111bba5596147a26cb    a/x

 B = master
    120000 blob a36b77384451ea1de7bd340ffca868249626bc52    a/b
    100644 blob e69de29bb2    a/b-2/c/d
    100644 blob e69de29bb2    a/x

With a clean index that matches HEAD, running

    git read-tree -m -u --aggressive $O $A $B

now yields

    120000 a36b77384451ea1de7bd340ffca868249626bc52 3       a/b
    100644 e69de29bb2 0       a/b-2/c/d
    100644 e69de29bb2 1       a/b/c/d
    100644 e69de29bb2 2       a/b/c/d
    100644 587be6b4c3f93f93c489c0111bba5596147a26cb 0       a/x

which is correct.  "master" created "a/b" symlink that did not exist,
and removed "a/b/c/d" while HEAD did not do touch either path.

Before this series, read-tree did not notice the situation and resolved
addition of "a/b" and removal of "a/b/c/d" independently.  If A = HEAD had
another path "a/b/c/e" added, this merge should conflict but instead it
silently resolved "a/b" and then immediately overwrote it to add
"a/b/c/e", which was quite bogus.

Tests in t1012 start to work with this.

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

15 years ago

Junio C Hamano

1ee26571e9

traverse_trees(): handle D/F conflict case sanely

traverse_trees() is supposed to call its callback with all the matching
entries from the given trees.  The current algorithm keeps a pointer to
each of the tree being traversed, and feeds the entry with the earliest
name to the callback.

This breaks down if the trees being traversed looks like this:

    A    B
    t-1  t
    t-2  u
    t/a  v

When we are currently looking at an entry "t-1" in tree A, and tree B has
returned "t", feeding "t" from the B and not feeding anything from A, only
because "t-1" sorts later than "t", will miss an entry for a subtree "t"
behind the current entry in tree A.

This introduces extended_entry_extract() helper function that gives what
name is expected from the tree, and implements a mechanism to look-ahead
in the tree object using it, to make sure such a case is handled sanely.
Traversal in tree A in the above example will first return "t" to match
that of B, and then the next request for an entry to A then returns "t-1".

This roughly corresponds to what Linus's "prepare for one-entry lookahead"
wanted to do, but because this does implement look ahead, t6035 and one more
test in t1012 reveal that the approach would not work without adjusting the
side that walks the index in unpack_trees() as well.

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

15 years ago

Junio C Hamano

934f930b31

more D/F conflict tests

Before starting to muck with this code, let's expose the current
breakages that we intend to fix.

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

15 years ago

3 Commits (cbf731ed4ec511f2c32598e03d7865f35881fea2)