Commits on Sep 9, 2021

1. diff: ignore sparse paths in diffstat …

   The diff_populate_filespec() method is used to describe the diff after a
   merge operation is complete. In order to avoid expanding a sparse index,
   the reuse_worktree_file() needs to be adapted to ignore files that are
   outside of the sparse-checkout cone. The file names and OIDs used for
   this check come from the merged tree in the case of the ORT strategy,
   not the index, hence the ability to look into these paths without having
   already expanded the index.
   
   The work done by reuse_worktree_file() is only an optimization, and
   requires the file being on disk for it to be of any value. Thus, it is
   safe to exit the method early if we do not expect the file on disk.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   ad90da7 View commit details

   Browse the repository at this point in the history

2. merge: make sparse-aware with ORT …

   Allow 'git merge' to operate without expanding a sparse index, at least
   not immediately. The index still will be expanded in a few cases:
   
   1. If the merge strategy is 'recursive', then we enable
      command_requires_full_index at the start of the merge_recursive()
      method. We expect sparse-index users to also have the 'ort' strategy
      enabled.
   
   2. With the 'ort' strategy, if the merge results in a conflicted file,
      then we expand the index before updating the working tree. The loop
      that iterates over the worktree replaces index entries and tracks
      'origintal_cache_nr' which can become completely wrong if the index
      expands in the middle of the operation. This safety valve is
      important before that loop starts. A later change will focus this
      to only expand if we indeed have a conflict outside of the
      sparse-checkout cone.
   
   3. Other merge strategies are executed as a 'git merge-X' subcommand,
      and those strategies are currently protected with the
      'command_requires_full_index' guard.
   
   Some test updates are required, including a mistaken 'git checkout -b'
   that did not specify the base branch, causing merges to be fast-forward
   merges.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   a338063 View commit details

   Browse the repository at this point in the history

3. merge-ort: expand only for out-of-cone conflicts …

   Merge conflicts happen often enough to want to avoid expanding a sparse
   index when they happen, as long as those conflicts are within the
   sparse-checkout cone. If a conflict exists outside of the
   sparse-checkout cone, then we still need to expand before iterating over
   the index entries. This is critical to do in advance because of how the
   original_cache_nr is tracked to allow inserting and replacing cache
   entries.
   
   Iterate over the conflicted files and check if any paths are outside of
   the sparse-checkout cone. If so, then expand the full index.
   
   Add a test that demonstrates that we do not expand the index, even when
   we hit a conflict within the sparse-checkout cone.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   6957636 View commit details

   Browse the repository at this point in the history

4. t1092: add cherry-pick, rebase tests …

   Add tests to check that cherry-pick and rebase behave the same in the
   sparse-index case as in the full index cases. These tests are agnostic
   to GIT_TEST_MERGE_ALGORITHM, so a full CI test suite will check both the
   'ort' and 'recursive' strategies on this test.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   c0b9930 View commit details

   Browse the repository at this point in the history

5. sequencer: ensure full index if not ORT strategy …

   The sequencer is used by 'cherry-pick' and 'rebase' to sequence a list
   of operations that modify the index. Since we intend to remove the need
   for 'command_requires_full_index', we need to ensure the sparse index is
   expanded every time it is written to disk between these steps. That is,
   unless the merge strategy is 'ort' where the index can remain sparse
   throughout.
   
   There are two main places to be extra careful about a full index:
   
   1. Right before calling merge_trees(), ensure the index is full. This
      happens within an 'else' where the 'if' block checks if the 'ort'
      strategy is selected.
   
   2. During read_and_refresh_cache(), the index might be written to disk
      and converted to sparse in the process. Ensure it expands back to
      full afterwards by checking if the strategy is _not_ 'ort'. This
      'if' statement is the logical negation of the 'if' in item (1).
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   5d9c934 View commit details

   Browse the repository at this point in the history

6. sparse-index: integrate with cherry-pick and rebase …

   The hard work was already done with 'git merge' and the ORT strategy.
   Just add extra tests to see that we get the expected results in the
   non-conflict cases.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
   Reviewed-by: Elijah Newren <newren@gmail.com>
   Signed-off-by: Junio C Hamano <gitster@pobox.com>

   

   derrickstolee authored and gitster committed Sep 9, 2021
   Copy the full SHA

   516680b View commit details

   Browse the repository at this point in the history