The "git_istream" abstraction has been revamped to make it easier
to interface with pluggable object database design.
* ps/object-read-stream:
streaming: drop redundant type and size pointers
streaming: move into object database subsystem
streaming: refactor interface to be object-database-centric
streaming: move logic to read packed objects streams into backend
streaming: move logic to read loose objects streams into backend
streaming: make the `odb_read_stream` definition public
streaming: get rid of `the_repository`
streaming: rely on object sources to create object stream
packfile: introduce function to read object info from a store
streaming: move zlib stream into backends
streaming: create structure for filtered object streams
streaming: create structure for packed object streams
streaming: create structure for loose object streams
streaming: create structure for in-core object streams
streaming: allocate stream inside the backend-specific logic
streaming: explicitly pass packfile info when streaming a packed object
streaming: propagate final object type via the stream
streaming: drop the `open()` callback function
streaming: rename `git_istream` into `odb_read_stream`
"git repo struct" learned to take "-z" as a synonym to "--format=nul".
* lo/repo-struct-z:
repo: add -z as an alias for --format=nul to git-repo-structure
repo: use [--format=... | -z] instead of [-z] in git-repo-info synopsis
repo: remove blank line from Documentation/git-repo.adoc
A help message from "git branch" now mentions "git help" instead of
"man" when suggesting to read some documentation.
* kh/advise-w-git-help-in-branch:
branch: advice using git-help(1) instead of man(1)
"git last-modified" used to mishandle "--" to mark the beginning of
pathspec, which has been corrected.
* js/last-modified-with-sparse-checkouts:
last-modified: support sparse checkouts
Recent optimization to "last-modified" command introduced use of
uninitialized block of memory, which has been corrected.
* tc/last-modified-active-paths-optimization:
last-modified: fix use of uninitialized memory
The use of "revision" (a connected set of commits) has been
clarified in the "git replay" documentation.
* en/replay-doc-revision-range:
Documentation/git-replay.adoc: fix errors around revision range
"git replay" forgot to omit the "gpgsig-sha256" extended header
from the resulting commit the same way it omits "gpgsig", which has
been corrected.
* pw/replay-exclude-gpgsig-fix:
replay: do not copy "gpgsign-sha256" header
The error message given by "git config set", when the variable
being updated has more than one values defined, used old style "git
config" syntax with an incorrect option in its hint, both of which
have been corrected.
* rs/config-set-multi-error-message-fix:
config: fix suggestion for failed set of multi-valued option
The option help text given by "git config unset -h" described
the "--all" option to "replace", not "unset", multiple variables,
which has been corrected.
* rs/config-unset-opthelp-fix:
config: fix short help of unset flags
Code refactoring around object database sources.
* ps/object-source-management:
odb: handle recreation of quarantine directories
odb: handle changing a repository's commondir
chdir-notify: add function to unregister listeners
odb: handle initialization of sources in `odb_new()`
http-push: stop setting up `the_repository` for each reference
t/helper: stop setting up `the_repository` repeatedly
builtin/index-pack: fix deferred fsck outside repos
oidset: introduce `oidset_equal()`
odb: move logic to disable ref updates into repo
odb: refactor `odb_clear()` to `odb_free()`
odb: adopt logic to close object databases
setup: convert `set_git_dir()` to have file scope
path: move `enter_repo()` into "setup.c"
"git config get --path" segfaulted on an ":(optional)path" that
does not exist, which has been corrected.
* jc/optional-path:
config: really treat missing optional path as not configured
config: really pretend missing :(optional) value is not there
config: mark otherwise unused function as file-scope static
Other Git commands that have nul-terminated output, such as git-config,
git-status, git-ls-files, and git-repo-info have a flag `-z` for using
the null character as the record separator.
Add the `-z` flag to git-repo-structure as an alias for `--format=nul`,
making it consistent with the behavior of the other commands.
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The flag -z is only an alias for --format=null and even though --format
and -z can be used together and repeated, only the last one is
considered.
Replace `[-z]` in the synopsis of git-repo-info by
`[--format=... | -z]`, expliciting that the use of one of those flags
replace the other.
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In a sparse checkout, a user might want to run `last-modified` on a
directory outside the worktree.
And even in non-sparse checkouts, a user might need to run that command
on a directory that does not exist in the worktree.
These use cases should be supported via the `--` separator between
revision and file arguments, which is even advertised in the
documentation. This patch fixes a tiny bug that prevents that from
working.
This fixes https://github.com/git-for-windows/git/issues/5978
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Derrick Stolee <stolee@gmail.com>
Acked-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
8fbd903e (branch: advise about ref syntax rules, 2024-03-05) added
an advice about checking git-check-ref-format(1) for the ref syntax
rules. The advice uses man(1). But git(1) is a multi-platform tool and
man(1) may not be available on some platforms. It might also be slightly
jarring to see a suggestion for running a command which is not from
the Git suite.
Let’s instead use git-help(1) in order to stay inside the land of
git(1). This also means that `help.format` (for `man`, `html` or other
formats) will be used if set.
Also change to using single quotes (') to quote the command since that
is more conventional.
While here let’s also update the test to use `{SQ}`, which is more
readable and easier to edit.
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-last-modified(1) uses a scratch bitmap to keep track of paths that
have been changed between commits. To avoid reallocating a bitmap on
each call of process_parent(), the scratch bitmap is kept and reused.
Although, it seems an incorrect length is passed to memset(3).
`struct bitmap` uses `eword_t` to for internal storage. This type is
typedef'd to uint64_t. To fully zero the memory used by the bitmap,
multiply the length (saved in `struct bitmap::word_alloc`) by the size
of `eword_t`.
Reported-by: Anders Kaseorg <andersk@mit.edu>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There was significant confusion in the git-replay manual about what
constitutes a revision range. As noted in f302c1e4aa09 (revisions(7):
clarify that most commands take a single revision range, 2021-05-18):
Commands that are specifically designed to take two distinct ranges
(e.g. "git range-diff R1 R2" to compare two ranges) do exist, but they
are exceptions. Unless otherwise noted, all "git" commands that operate
on a set of commits work on a single revision range.
`git replay` is not an exception, but a few places in the manual were
written as though it were. These appear to have come in revisions to
the original series, between v3->v4 (see
https://lore.kernel.org/git/CAP8UFD3bpLrVW97DH7j=V9H2GsTSAkksC9L3QujQERFk_kLnZA@mail.gmail.com/
, "More than one <revision-range> can be passed") and between v6->v7
(https://lore.kernel.org/git/20231115143327.2441397-1-christian.couder@gmail.com/,
"Takes ranges of commits"), and I missed both of these revisions when
reviewing. Fix them now.
There was also a reference to the "Commit Limiting options below", but
this page has no such section of options; strike the misleading
reference.
It is worth noting that we are documenting existing behavior, rather
than optimal behavior. Junio has multiple times suggested introducing
alternative ways to walk revisions and use them in `git replay
--advance`, e.g. at
* https://lore.kernel.org/git/xmqqy1mqo6kv.fsf@gitster.g/
* https://lore.kernel.org/git/xmqq8rb3is8c.fsf@gitster.g/
* https://lore.kernel.org/git/xmqqtsydj2zk.fsf@gitster.g/ (item (2))
If/when we introduce some new revision walking flag that implements one
of these alternate types of revision walks, we can update the --advance
option and this manual appropriately.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git worktree list" attempts to show paths to worktrees while
aligning them, but miscounted display columns for the paths when
non-ASCII characters were involved, which has been corrected.
* pw/worktree-list-display-width-fix:
worktree list: quote paths
worktree list: fix column spacing
When "git replay" replays a commit it copies the extended headers
across from the original commit. However, if the original commit
was signed, we do not want to copy the header associated with the
signature is it wont be valid for the new commit. The code already
knows to avoid coping the "gpgsig" header but does not know to avoid
copying the "gpgsig-sha256" header. Add that header to the list of
exclusions to match what "git commit --amend" does.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Tools like `git filter-repo`[1] use `git fast-export` and
`git fast-import` to rewrite repository history. When rewriting
history using one such tool though, commit signatures might become
invalid because the commits they sign changed due to the changes
in the repository history made by the tool between the fast-export
and the fast-import steps.
Note that as far as signature handling goes:
* Since fast-export doesn't know what changes filter-repo may make
to the stream, it can't know whether the signatures will still be
valid.
* Since filter-repo doesn't know what history canonicalizations
fast-export performed (and it performs a few), it can't know whether
the signatures will still be valid.
* Therefore, fast-import is the only process in the pipeline that
can know whether a specified signature remains valid.
Having invalid signatures in a rewritten repository could be
confusing, so users rewritting history might prefer to simply
discard signatures that are invalid at the fast-import step.
For example a common use case is to rewrite only "recent" history.
While specifying commit ranges corresponding to "recent" commits
could work, users worry about getting it wrong and want to just
automatically rewrite everything, expecting older commit signatures
to be untouched.
To let them do that, let's add a new 'strip-if-invalid' mode to the
`--signed-commits=<mode>` option of `git fast-import`.
It would be interesting for the `--signed-tags=<mode>` option to
have this mode too, but we leave that for a future improvement.
It might also be possible for `git fast-export` to have such a mode
in its `--signed-commits=<mode>` and `--signed-tags=<mode>`
options, but the use cases for it are much less clear, so we also
leave that for possible future improvements.
For now let's just die() if 'strip-if-invalid' is passed to these
options where it hasn't been implemented yet.
[1]: https://github.com/newren/git-filter-repo
Helped-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When asked to perform object consistency checks via the `--fsck-objects`
flag we verify that each object part of the pack is valid. In general,
this check can even be performed outside of a Git repository: we don't
need an initialized object database as we simply read the object from
the packfile directly.
But there's one exception: a subset of the object checks may be deferred
to a later point in time. For now, this only concerns ".gitmodules" and
".gitattributes" files: whenever we see a tree referencing these files
we queue them for a deferred check. This is done because we need to do
some extra checks for those files to ensure that they are well-formed,
and these checks need to be done regardless of whether the corresponding
blobs are part of the packfile or not.
This works inside a repository, but unfortunately the logic leads to a
segfault when running outside of one. This is because we eventually call
`odb_read_object()`, which will crash because the object database has
not been initialized.
There's multiple options here:
- We could in theory create a purely in-memory database with only a
packfile store that contains the single packfile. We don't really
have the infrastructure for this yet though, and it would end up
being quite hacky.
- We could refuse to perform consistency checks outside of a
repository. But most of the checks work alright, so this would be a
regression.
- We can skip the finalizing consistency checks when running outside
of a repository. This is not as invasive as skipping all checks,
but it's not great to randomly skip a subset of tests, either.
None of these options really feel perfect. The first one would be the
obvious choice if easily possible.
There's another option though: instead of skipping the final object
checks, we can die if there are any queued object checks. With this
change we now die exactly if and only if we would have previously
segfaulted. Like this we ensure that objects that _may_ fail the
consistency checks won't be silently skipped, and at the same time we
give users a much better error message.
Refactor the code accordingly and add a test that would have triggered
the segfault. Note that we also move down the logic to add the packfile
to the store. There is no point doing this any earlier than right before
we execute `fsck_finish()`, and it ensures that the logic to set up and
perform the consistency check is self-contained.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These callers expect that git_config_pathname() that returns 0 is a
signal that the variable they passed has a string they need to act
on. But with the introduction of ":(optional)path" earlier, that is
no longer the case. If the path specified by the configuration
variable is missing, their variable will get a NULL in it, and they
need to act on it (often, just refraining from copying it elsewhere).
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Earlier we added support for a value spelled as ":(optional)path"
for configuration variables whose values are of type "path", with
the documented semantics "if the path is missing, behave as if such
a variable definition is not even there."
This has worked OK for code paths that reads configuration files and
stores the configured value as a string, where NULL in such a string
is treated as if the setting is not there, left as the default.
However, there are other code paths that do not _ignore_ such NULL
values and misbehave. "git config get --path" is one of them.
When git_config_pathname() helper function finds that the value of
the variable is an optional path *and* the path is missing, it
leaves the destination pointer intact (which usually is left to
NULL) and returns 0 to signal a success. format_config() helper
however assumed that the destination pointer always gets a string,
which no longer is the case, and segfaulted.
Make sure that git_config_pathname() clears the destination pointer
in such a case, and teach format_config() to react to the condition
by returning 1 (which is different from 0 that is a normal success
and negative that is an error) to its callers. Adjust the callers
to react to this new return value that tells them to pretend as if
they did not even see this partcular <key, value> pair.
Reported-by: Han Jiang <jhcarl0814@gmail.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "git repo structure" subcommand tried to align its output but
mixed up byte count and display column width, which has been
corrected.
* jx/repo-struct-utf8width-fix:
builtin/repo: fix table alignment for UTF-8 characters
t/unit-tests: add UTF-8 width tests for CJK chars
A part of code paths that deals with loose objects has been cleaned
up.
* ps/object-source-loose:
object-file: refactor writing objects via a stream
object-file: rename `write_object_file()`
object-file: refactor freshening of objects
object-file: rename `has_loose_object()`
object-file: read objects via the loose object source
object-file: move loose object map into loose source
object-file: hide internals when we need to reprepare loose sources
object-file: move loose object cache into loose source
object-file: introduce `struct odb_source_loose`
object-file: move `fetch_if_missing`
odb: adjust naming to free object sources
odb: introduce `odb_source_new()`
odb: fix subtle logic to check whether an alternate is usable
"git replay" (experimental) learned to perform ref updates itself
in a transaction by default, instead of emitting where each refs
should point at and leaving the actual update to another command.
* sa/replay-atomic-ref-updates:
replay: add replay.refAction config option
replay: make atomic ref updates the default behavior
replay: use die_for_incompatible_opt2() for option validation
The flags --all and --value of "git config unset" don't make the command
"replace" or "show" anything, they are about selecting what to unset.
Change their help text accordingly.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The command "git config set <name> <value>" fails for an option that has
multiple values. List the "git config set" flags that can be used,
instead of old-style "git config" actions.
Reported-by: Paul Wintz <pwintz@ucsc.edu>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the preceding commits we have turned `struct odb_read_stream` into a
publicly visible structure. Furthermore, this structure now contains the
type and size of the object that we are about to stream. Consequently,
the out-pointers that we used before to propagate the type and size of
the streamed object are now somewhat redundant with the data contained
in the structure itself.
Drop these out-pointers and adapt callers accordingly.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "streaming" terminology is somewhat generic, so it may not be
immediately obvious that "streaming.{c,h}" is specific to the object
database. Rectify this by moving it into the "odb/" directory so that it
can be immediately attributed to the object subsystem.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Refactor the streaming interface to be centered around object databases
instead of centered around the repository. Rename the functions
accordingly.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Subsequent commits will move the backend-specific logic of object
streaming into their respective subsystems. These subsystems have gotten
rid of `the_repository` already, but we still use it in two locations in
the streaming subsystem.
Prepare for the move by fixing those two cases. Converting the logic in
`open_istream_pack_non_delta()` is trivial as we already got the object
database as input.
But for `stream_blob_to_fd()` we have to add a new parameter to make it
accessible. So, as we already have to adjust all callers anyway, rename
the function to `odb_stream_blob_to_fd()` to indicate it's part of the
object subsystem.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the following patches we are about to make the `git_istream` more
generic so that it becomes fully controlled by the specific object
source that wants to create it. As part of these refactorings we'll
fully move the structure into the object database subsystem.
Prepare for this change by renaming the structure from `git_istream`
to `odb_read_stream`. This mirrors the `odb_write_stream` structure that
we already have.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git maintenance" command learned "is-needed" subcommand to tell if
it is necessary to perform various maintenance tasks.
* kn/maintenance-is-needed:
maintenance: add 'is-needed' subcommand
maintenance: add checking logic in `pack_refs_condition()`
refs: add a `optimize_required` field to `struct ref_storage_be`
reftable/stack: add function to check if optimization is required
reftable/stack: return stack segments directly
The logic to close an object database is currently contained in the
packfile subsystem. That choice is somewhat relatable, as most of the
logic really is to close resources associated with the packfile store
itself. But we also end up handling object sources and commit graphs,
which certainly is not related to packfiles.
Move the function into the object database subsystem and rename it to
`odb_close()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function `enter_repo()` is used to enter a repository at a given
path. As such it sits way closer to setting up a repository than it does
with handling paths, but regardless of that it's located in "path.c"
instead of in "setup.c".
Move the function into "setup.c".
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A part of code paths that deals with loose objects has been cleaned
up.
* ps/object-source-loose:
object-file: refactor writing objects via a stream
object-file: rename `write_object_file()`
object-file: refactor freshening of objects
object-file: rename `has_loose_object()`
object-file: read objects via the loose object source
object-file: move loose object map into loose source
object-file: hide internals when we need to reprepare loose sources
object-file: move loose object cache into loose source
object-file: introduce `struct odb_source_loose`
object-file: move `fetch_if_missing`
odb: adjust naming to free object sources
odb: introduce `odb_source_new()`
odb: fix subtle logic to check whether an alternate is usable
A part of code paths that deals with loose objects has been cleaned
up.
* ps/object-source-loose:
object-file: refactor writing objects via a stream
object-file: rename `write_object_file()`
object-file: refactor freshening of objects
object-file: rename `has_loose_object()`
object-file: read objects via the loose object source
object-file: move loose object map into loose source
object-file: hide internals when we need to reprepare loose sources
object-file: move loose object cache into loose source
object-file: introduce `struct odb_source_loose`
object-file: move `fetch_if_missing`
odb: adjust naming to free object sources
odb: introduce `odb_source_new()`
odb: fix subtle logic to check whether an alternate is usable
- Switch the synopsis to a synopsis block which will automatically
format placeholders in italics and keywords in monospace
- Use _<placeholder>_ instead of <placeholder> in the description
- Use `backticks` for keywords and more complex option
descriptions. The new rendering engine will apply synopsis rules to
these spans.
Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some ref backend storage can hold not just the object name of an
annotated tag, but the object name of the object the tag points at.
The code to handle this information has been streamlined.
* ps/ref-peeled-tags:
t7004: do not chdir around in the main process
ref-filter: fix stale parsed objects
ref-filter: parse objects on demand
ref-filter: detect broken tags when dereferencing them
refs: don't store peeled object IDs for invalid tags
object: add flag to `peel_object()` to verify object type
refs: drop infrastructure to peel via iterators
refs: drop `current_ref_iter` hack
builtin/show-ref: convert to use `reference_get_peeled_oid()`
ref-filter: propagate peeled object ID
upload-pack: convert to use `reference_get_peeled_oid()`
refs: expose peeled object ID via the iterator
refs: refactor reference status flags
refs: fully reset `struct ref_iterator::ref` on iteration
refs: introduce `.ref` field for the base iterator
refs: introduce wrapper struct for `each_ref_fn`
The list of packfiles used in a running Git process is moved from
the packed_git structure into the packfile store.
* ps/packed-git-in-object-store:
packfile: track packs via the MRU list exclusively
packfile: always add packfiles to MRU when adding a pack
packfile: move list of packs into the packfile store
builtin/pack-objects: simplify logic to find kept or nonlocal objects
packfile: fix approximation of object counts
http: refactor subsystem to use `packfile_list`s
packfile: move the MRU list into the packfile store
packfile: use a `strmap` to store packs by name
Add a new flag `--all` to git-repo-info for requesting values for all
the available keys. By using this flag, the user can retrieve all the
values instead of searching what are the desired keys for what they
wants.
Helped-by: Karthik Nayak <karthik.188@gmail.com>
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the field printing in git-repo-info to a new function called
`print_field`, allowing it to be called by functions other than
`print_fields`.
Also change its use of quote_c_style() helper to output directly to
the standard output stream, instead of taking a result in a strbuf
and then printing it outselves.
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a worktree path contains newlines or other control characters
it messes up the output of "git worktree list". Fix this by using
quote_path() to display the worktree path. The output of "git worktree
list" is designed for human consumption, scripts should be using the
"--porcelain" option so this change should not break them.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The output of "git worktree list" displays a table containing the
worktree path, HEAD OID and branch name for each worktree. The code
aligns the columns by measuring the visual width of the worktree path
when it is printed. Unfortunately it fails to use the visual width
when calculating the width of the column so, if any of the paths
contain a multibyte character, we can end up with excess padding
between columns. The simplest fix would be to replace strlen() with
utf8_strwidth() in measure_widths(). However that leaves us measuring
the visual width twice and the byte length once. By caching the visual
width and printing the padding separately to the worktree path, we only
need to calculate the visual width once and do not need the byte length
at all. The visual widths are stored in an arrays of structs rather
than an array of ints as the next commit will add more struct members.
Even if there are no multibyte characters in any of the paths we still
print an extra space between the path and the object id as the field
width is calculated as one plus the length of the path and we print an
explicit space as well. This is fixed by not printing the extra space.
The tests are updated to include multibyte characters in one of the
worktree paths and to check the spacing of the columns.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The diff algorithm used in 'git-blame(1)' is set to 'myers',
without the possibility to change it aside from the `--minimal` option.
There has been long-standing interest in changing the default diff
algorithm to "histogram", and Git 3.0 was floated as a possible occasion
for taking some steps towards that:
https://lore.kernel.org/git/xmqqed873vgn.fsf@gitster.g/
As a preparation for this move, it is worth making sure that the diff
algorithm is configurable where useful.
Make it configurable in the `git-blame(1)` command by introducing the
`--diff-algorithm` option and make honor the `diff.algorithm` config
variable. Keep Myers diff as the default.
Signed-off-by: Antonin Delpeuch <antonin@delpeuch.eu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
