The default file history simplification of "git log -- <path>" or
"git rev-list -- <path>" focuses on providing the smallest set of
commits that first contributed a change. The revision walk greatly
restricts the set of walked commits by visiting only the first
TREESAME parent of a merge commit, when one exists. This means
that portions of the commit-graph are not walked, which can be a
performance benefit, but can also "hide" commits that added changes
but were ignored by a merge resolution.
The --full-history option modifies this by walking all commits and
reporting a merge commit as "interesting" if it has _any_ parent
that is not TREESAME. This tends to be an over-representation of
important commits, especially in an environment where most merge
commits are created by pull request completion.
Suppose we have a commit A and we create a commit B on top that
changes our file. When we merge the pull request, we create a merge
commit M. If no one else changed the file in the first-parent
history between M and A, then M will not be TREESAME to its first
parent, but will be TREESAME to B. Thus, the simplified history
will be "B". However, M will appear in the --full-history mode.
However, suppose that a number of topics T1, T2, ..., Tn were
created based on commits C1, C2, ..., Cn between A and M as
follows:
A----C1----C2--- ... ---Cn----M------P1---P2--- ... ---Pn
\ \ \ \ / / / /
\ \__.. \ \/ ..__T1 / Tn
\ \__.. /\ ..__T2 /
\_____________________B \____________________/
If the commits T1, T2, ... Tn did not change the file, then all of
P1 through Pn will be TREESAME to their first parent, but not
TREESAME to their second. This means that all of those merge commits
appear in the --full-history view, with edges that immediately
collapse into the lower history without introducing interesting
single-parent commits.
The --simplify-merges option was introduced to remove these extra
merge commits. By noticing that the rewritten parents are reachable
from their first parents, those edges can be simplified away. Finally,
the commits now look like single-parent commits that are TREESAME to
their "only" parent. Thus, they are removed and this issue does not
cause issues anymore. However, this also ends up removing the commit
M from the history view! Even worse, the --simplify-merges option
requires walking the entire history before returning a single result.
Many Git users are using Git alongside a Git service that provides
code storage alongside a code review tool commonly called "Pull
Requests" or "Merge Requests" against a target branch. When these
requests are accepted and merged, they typically create a merge
commit whose first parent is the previous branch tip and the second
parent is the tip of the topic branch used for the request. This
presents a valuable order to the parents, but also makes that merge
commit slightly special. Users may want to see not only which
commits changed a file, but which pull requests merged those commits
into their branch. In the previous example, this would mean the
users want to see the merge commit "M" in addition to the single-
parent commit "C".
Users are even more likely to want these merge commits when they
use pull requests to merge into a feature branch before merging that
feature branch into their trunk.
In some sense, users are asking for the "first" merge commit to
bring in the change to their branch. As long as the parent order is
consistent, this can be handled with the following rule:
Include a merge commit if it is not TREESAME to its first
parent, but is TREESAME to a later parent.
These merges look like the merge commits that would result from
running "git pull <topic>" on a main branch. Thus, the option to
show these commits is called "--show-pulls". This has the added
benefit of showing the commits created by closing a pull request or
merge request on any of the Git hosting and code review platforms.
To test these options, extend the standard test example to include
a merge commit that is not TREESAME to its first parent. It is
surprising that that option was not already in the example, as it
is instructive.
In particular, this extension demonstrates a common issue with file
history simplification. When a user resolves a merge conflict using
"-Xours" or otherwise ignoring one side of the conflict, they create
a TREESAME edge that probably should not be TREESAME. This leads
users to become frustrated and complain that "my change disappeared!"
In my experience, showing them history with --full-history and
--simplify-merges quickly reveals the problematic merge. As mentioned,
this option is expensive to compute. The --show-pulls option
_might_ show the merge commit (usually titled "resolving conflicts")
more quickly. Of course, this depends on the user having the correct
parent order, which is backwards when using "git pull master" from a
topic branch.
There are some special considerations when combining the --show-pulls
option with --simplify-merges. This requires adding a new PULL_MERGE
object flag to store the information from the initial TREESAME
comparisons. This helps avoid dropping those commits in later filters.
This is covered by a test, including how the parents can be simplified.
Since "struct object" has already ruined its 32-bit alignment by using
33 bits across parsed, type, and flags member, let's not make it worse.
PULL_MERGE is used in revision.c with the same value (1u<<15) as
REACHABLE in commit-graph.c. The REACHABLE flag is only used when
writing a commit-graph file, and a revision walk using --show-pulls
does not happen in the same process. Care must be taken in the future
to ensure this remains the case.
Update Documentation/rev-list-options.txt with significant details
around this option. This requires updating the example in the
History Simplification section to demonstrate some of the problems
with TREESAME second parents.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The 'pack.useSparse' configuration variable now defaults to 'true',
enabling an optimization that has been experimental since Git 2.21.
* ds/default-pack-use-sparse-to-true:
pack-objects: flip the use of GIT_TEST_PACK_SPARSE
config: set pack.useSparse=true by default
"git pull" learned to warn when no pull.rebase configuration
exists, and neither --[no-]rebase nor --ff-only is given (which
would result a merge).
* ah/force-pull-rebase-configuration:
pull: warn if the user didn't say whether to rebase or to merge
"git stash" has kept an escape hatch to use the scripted version
for a few releases, which got stale. It has been removed.
* tg/retire-scripted-stash:
stash: remove the stash.useBuiltin setting
stash: get git_stash_config at the top level
When "git describe C" finds an annotated tag with tagname A to be
the best name to explain commit C, and the tag is stored in a
"wrong" place in the refs/tags hierarchy, e.g. refs/tags/B, the
command gave a warning message but used A (not B) to describe C.
If C is exactly at the tag, the describe output would be "A", but
"git rev-parse A^0" would not be equal as "git rev-parse C^0". The
behavior of the command has been changed to use the "long" form
i.e. A-0-gOBJECTNAME, which is correctly interpreted by rev-parse.
* jc/describe-misnamed-annotated-tag:
describe: force long format for a name based on a mislocated tag
The "--fork-point" mode of "git rebase" regressed when the command
was rewritten in C back in 2.20 era, which has been corrected.
* at/rebase-fork-point-regression-fix:
rebase: --fork-point regression fix
Provide more information (e.g. the object of the tree-ish in which
the blob being converted appears, in addition to its path, which
has already been given) to smudge/clean conversion filters.
* bc/filter-process:
t0021: test filter metadata for additional cases
builtin/reset: compute checkout metadata for reset
builtin/rebase: compute checkout metadata for rebases
builtin/clone: compute checkout metadata for clones
builtin/checkout: compute checkout metadata for checkouts
convert: provide additional metadata to filters
convert: permit passing additional metadata to filter processes
builtin/checkout: pass branch info down to checkout_worktree
The code to interface with GnuPG has been refactored.
* hi/gpg-prefer-check-signature:
gpg-interface: prefer check_signature() for GPG verification
t: increase test coverage of signature verification output
SHA-256 transition continues.
* bc/sha-256-part-1-of-4: (22 commits)
fast-import: add options for rewriting submodules
fast-import: add a generic function to iterate over marks
fast-import: make find_marks work on any mark set
fast-import: add helper function for inserting mark object entries
fast-import: permit reading multiple marks files
commit: use expected signature header for SHA-256
worktree: allow repository version 1
init-db: move writing repo version into a function
builtin/init-db: add environment variable for new repo hash
builtin/init-db: allow specifying hash algorithm on command line
setup: allow check_repository_format to read repository format
t/helper: make repository tests hash independent
t/helper: initialize repository if necessary
t/helper/test-dump-split-index: initialize git repository
t6300: make hash algorithm independent
t6300: abstract away SHA-1-specific constants
t: use hash-specific lookup tables to define test constants
repository: require a build flag to use SHA-256
hex: add functions to parse hex object IDs in any algorithm
hex: introduce parsing variants taking hash algorithms
...
Fix "git checkout --recurse-submodules" of a nested submodule
hierarchy.
* pb/recurse-submodules-fix:
t/lib-submodule-update: add test removing nested submodules
unpack-trees: check for missing submodule directory in merged_entry
unpack-trees: remove outdated description for verify_clean_submodule
t/lib-submodule-update: move a test to the right section
t/lib-submodule-update: remove outdated test description
t7112: remove mention of KNOWN_FAILURE_SUBMODULE_RECURSIVE_NESTED
The mechanism to prevent "git commit" from making an empty commit
or amending during an interrupted cherry-pick was broken during the
rewrite of "git rebase" in C, which has been corrected.
* pw/advise-rebase-skip:
commit: give correct advice for empty commit during a rebase
commit: encapsulate determine_whence() for sequencer
commit: use enum value for multiple cherry-picks
sequencer: write CHERRY_PICK_HEAD for reword and edit
cherry-pick: check commit error messages
cherry-pick: add test for `--skip` advice in `git commit`
t3404: use test_cmp_rev
Update "git p4" to work with Python 3.
* yz/p4-py3:
ci: use python3 in linux-gcc and osx-gcc and python2 elsewhere
git-p4: use python3's input() everywhere
git-p4: simplify regex pattern generation for parsing diff-tree
git-p4: use dict.items() iteration for python3 compatibility
git-p4: use functools.reduce instead of reduce
git-p4: fix freezing while waiting for fast-import progress
git-p4: use marshal format version 2 when sending to p4
git-p4: open .gitp4-usercache.txt in text mode
git-p4: convert path to unicode before processing them
git-p4: encode/decode communication with git for python3
git-p4: encode/decode communication with p4 for python3
git-p4: remove string type aliasing
git-p4: change the expansion test from basestring to list
git-p4: make python2.7 the oldest supported version
The real_path() convenience function can easily be misused; with a
bit of code refactoring in the callers' side, its use has been
eliminated.
* am/real-path-fix:
get_superproject_working_tree(): return strbuf
real_path_if_valid(): remove unsafe API
real_path: remove unsafe API
set_git_dir: fix crash when used with real_path()
A handful of options to configure SSL when talking to proxies have
been added.
* js/https-proxy-config:
http: add environment variable support for HTTPS proxies
http: add client cert support for HTTPS proxies
Revamping of the advise API to allow more systematic enumeration of
advice knobs in the future.
* hw/advise-ng:
tag: use new advice API to check visibility
advice: revamp advise API
advice: change "setupStreamFailure" to "setUpstreamFailure"
advice: extract vadvise() from advise()
This test runs a function which itself runs several assertions. The
last of these assertions cleans up the .git/rebase-apply directory,
since when run with EXPENSIVE set, the function is invoked a second time
to run the same tests with a larger data set.
However, as of 2ac0d6273f ("rebase: change the default backend from "am"
to "merge"", 2020-02-15), the default backend of rebase has changed, and
cleaning up the rebase-apply directory has no effect: it no longer
exists, since we're using rebase-merge instead.
Since we don't really care which rebase backend is in use, let's just
use the command "git rebase --quit", which will do the right thing
regardless.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The environment variable GIT_TEST_PACK_SPARSE was previously used
to allow testing the --sparse option for "git pack-objects" in
the test suite. This allowed interesting cases of "git push" to
also test this algorithm.
Since pack.useSparse is now true by default, we do not need this
variable to _enable_ the --sparse option, but instead to _disable_
it. This flips how we work with the variable a bit.
When checking for the variable, default to a value of -1 for
"unset". If unset, then take the default from the repo settings,
which is currently 1. Then, the --[no-]sparse command-line option
will override either of these settings.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The pack.useSparse config option was introduced by 3d036eb0
(pack-objects: create pack.useSparse setting, 2019-01-19) and was
first available in v2.21.0. When enabled, the pack-objects process
during 'git push' will use a sparse tree walk when deciding which
trees and blobs to send to the remote. The algorithm was introduced
by d5d2e93 (revision: implement sparse algorithm, 2019-01-16) and
has been in production use by VFS for Git since around that time.
The features.experimental config option also enabled pack.useSparse,
so hopefully that has also increased exposure.
It is worth noting that pack.useSparse has a possibility of
sending more objects across a push, but requires a special
arrangement of exact _copies_ across directories. There is a test
in t5322-pack-objects-sparse.sh that demonstrates this possibility.
This test uses the --sparse option to "git pack-objects" but we
can make it implied by the config value to demonstrate that the
default value has changed.
While updating that test, I noticed that the documentation did not
include an option for --no-sparse, which is now more important than
it was before.
Since the downside is unlikely but the upside is significant, set
the default value of pack.useSparse to true. Remove it from the
set of options implied by features.experimental.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* 'master' of https://github.com/prati0100/git-gui:
git-gui: create a new namespace for chord script evaluation
git-gui: reduce Tcl version requirement from 8.6 to 8.5
git-gui--askpass: coerce answers to UTF-8 on Windows
git-gui: fix error popup when doing blame -> "Show History Context"
git-gui: add missing close bracket
git-gui: update German translation
git-gui: extend translation glossary template with more terms
git-gui: update pot template and German translation to current source code
Reduce the Tcl version requirement to 8.5 to allow git-gui to run on
MacOS distributions like High Sierra. While here, fix a potential
variable name collision.
* py/remove-tcloo:
git-gui: create a new namespace for chord script evaluation
git-gui: reduce Tcl version requirement from 8.6 to 8.5
In 'submodule--helper.c', the structures and macros for callbacks belonging
to any subcommand are named in the format: 'subcommand_cb' and 'SUBCOMMAND_CB_INIT'
respectively.
This was an exception for the subcommand 'foreach' of the command
'submodule'. Rename the aforementioned structures and macros:
'struct cb_foreach' to 'struct foreach_cb' and 'CB_FOREACH_INIT'
to 'FOREACH_CB_INIT'.
Signed-off-by: Shourya Shukla <shouryashukla.oo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Even though there is only one configuration variable in the
namespace, it is not quite right to have tar.umask described
among the variables for tag.* namespace.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Updates to the CI settings.
* js/ci-windows-update:
Azure Pipeline: switch to the latest agent pools
ci: prevent `perforce` from being quarantined
t/lib-httpd: avoid using macOS' sed
