Wip diff endpoints v07#6
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Test clean-up. * pb/t4200-test-path-is-helpers: t4200: convert test -[df] checks to test_path_* helpers
Test clean-up. * mf/t0008-cleanup: t0008: improve test cleanup to fix failing test
The final clean-up phase of the diff output could turn the result of histogram diff algorithm suboptimal, which has been corrected. * yc/histogram-hunk-shift-fix: xdiff: re-diff shifted change groups when using histogram algorithm
Reduce system overhead "git upload-pack" spends on relaying "git pack-objects" output to the "git fetch" running on the other end of the connection. * ps/upload-pack-buffer-more-writes: builtin/pack-objects: reduce lock contention when writing packfile data csum-file: drop `hashfd_throughput()` csum-file: introduce `hashfd_ext()` sideband: use writev(3p) to send pktlines wrapper: introduce writev(3p) wrappers compat/posix: introduce writev(3p) wrapper upload-pack: reduce lock contention when writing packfile data upload-pack: prefer flushing data over sending keepalive upload-pack: adapt keepalives based on buffering upload-pack: fix debug statement when flushing packfile data
"git diff -U<num>" was too lenient in its command line parsing and took an empty string as a valid <num>. * ty/doc-diff-u-wo-number: diff: document -U without <n> as using default context
Add a coccinelle rule to break the build when "struct strbuf" gets passed by value. * dd/cocci-do-not-pass-strbuf-by-value: stash: do not pass strbuf by value coccinelle: detect struct strbuf passed by value
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-replay(1) doesn't allow replaying commits all the way down to the root commit. Fix that. Signed-off-by: Toon Claes <toon@iotcl.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
The test added by 71f4960 (t0061: fix test for argv[0] with spaces (MINGW only), 2019-10-01) checks that we can use a .bat file with spaces as GIT_SSH. This is a good test in the sense that it's how the original bug was detected. And as the commit message there describes, there are some elements of the bug that are likely to come up with GIT_SSH and not elsewhere: namely that in addition to the .bat file having spaces, we must pass an argument with spaces (which happens naturally with ssh, since we pass the upload-pack shell command for the other side to run). But using GIT_SSH does complicate matters: 1. We actually run the ssh command _twice_, once to probe the ssh variant with "-G" in fill_ssh_args(), and then a second time to actually make the connection. So we have to account for that when checking the output. 2. Our fake ssh .bat file does not actually run ssh. So we expect the command to fail, but not before the .bat file has touched the "out" marker file that tells us it has run. This works now, but is fragile. In particular, the .bat file by default will echo commands it runs to stdout. From the perspective of the parent Git process, this is protocol-breaking garbage, and upon seeing it will die(). That is OK for now because we don't bother to do any cleanup of the child process. But there is a patch under discussion, dd3693e (transport-helper, connect: use clean_on_exit to reap children on abnormal exit, 2026-03-12), which causes us to kill() the .bat process. This happens before it actually touches the "out" file, causing the test to fail. We can simplify this by just using the "test-tool run-command" helper. That lets us run whatever command we like with the arguments we want. The argument here has a space, which is enough to trigger the original bug that 71f4960 was testing. I verified that by reverting eb7c786 (mingw: support spawning programs containing spaces in their names, 2019-07-16), the original fix, and confirming that the test fails (but succeeds without the revert). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Factor the "git repo info" and "git repo structure" usage strings into shared macros so they can be reused in multiple usage arrays. This is a preparatory refactoring for subsequent changes to subcommand-specific help output. Signed-off-by: Mahi Kassa <mahlet.takassa@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Use subcommand-specific usage arrays for "git repo info" and "git repo structure" so that each command shows only its own synopsis in help output. Add tests to cover the subcommand help behavior. Signed-off-by: Mahi Kassa <mahlet.takassa@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Further work on incremental repacking using MIDX/bitmap * tb/incremental-midx-part-3.2: midx: enable reachability bitmaps during MIDX compaction midx: implement MIDX compaction t/helper/test-read-midx.c: plug memory leak when selecting layer midx-write.c: factor fanout layering from `compute_sorted_entries()` midx-write.c: enumerate `pack_int_id` values directly midx-write.c: extract `fill_pack_from_midx()` midx-write.c: introduce `midx_pack_perm()` helper midx: do not require packs to be sorted in lexicographic order midx-write.c: introduce `struct write_midx_opts` midx-write.c: don't use `pack_perm` when assigning `bitmap_pos` t/t5319-multi-pack-index.sh: fix copy-and-paste error in t5319.39 git-multi-pack-index(1): align SYNOPSIS with 'git multi-pack-index -h' git-multi-pack-index(1): remove non-existent incompatibility builtin/multi-pack-index.c: make '--progress' a common option midx: introduce `midx_get_checksum_hex()` midx: rename `get_midx_checksum()` to `midx_get_checksum_hash()` midx: mark `get_midx_checksum()` arguments as const
The logic to count objects has been cleaned up. * ps/object-counting: odb: introduce generic object counting odb/source: introduce generic object counting object-file: generalize counting objects object-file: extract logic to approximate object count packfile: extract logic to count number of objects odb: stop including "odb/source.h"
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the convenience wrapper from hook to string-list since it's a more suitable place. Add a doc comment to the header. Also add a free_util arg to make the function more generic and make the API similar to other functions in string-list.h. Update the existing call-sites. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
The run_receive_hook() stack-allocated `struct receive_hook_feed_state` is a template with initial values for child states allocated on the heap for each hook process, by calling receive_hook_feed_state_alloc() when spinning up each hook child. All these values are already initialized to zero, however I forgot to properly initialize the strbuf, which I left NULL. This is more of a code cleanup because in practice it has no effect, the states used by the children are always initialized, however it's good to fix in case someone ends up accidentally dereferencing the NULL pointer in the future. Reported-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix some minor style nits pointed out by Patrick, Junio and Eric: * Use CALLOC_ARRAY instead of xcalloc. * Init struct members during declaration. * Simplify if condition boolean logic. * Missing curly braces in if/else stmts. * Unnecessary header includes. * Capitalization and full-stop in error/warn messages. * Curly brace on separate line when defining struct. * Comment spelling: free'd -> freed. * Sort the included headers. * Blank line fixes to improve readability. These contain no logic changes, the code behaves the same as before. Suggested-by: Eric Sunshine <sunshine@sunshineco.com> Suggested-by: Junio C Hamano <gitster@pobox.com> Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rename the hook callback function types to use the hook prefix. This is a style fix with no logic changes. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Trigger a bug when an unknown hook type is encountered while setting up hook execution. Also issue a bug if a configured hook is enabled without a cmd. Mostly useful for defensive coding. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Replace the custom function with string_list_clear_func() which is a more common pattern for clearing a string_list. To be able to do this, rework hook_clear() into hook_free(), so it can be passed to string_list_clear_func(). A slight complication is the need to keep a copy of the internal cb data free() pointer, however I think it's worth it since the API becomes cleaner, e.g. no more calls with NULL function args like hook_list_clear(hooks, NULL). In other words, the callers don't need to keep track of hook internal state to determine when cleanup is necessary or not (pass NULL) because each `struct hook` now owns its data_free callback. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Both `name` and `friendly-name` is being used. Standardize on `friendly-name` for consistency since name is rather generic, even when used in the hooks namespace. Suggested-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
There is a documented expectation that configured hooks are run before the hook from the hookdir. Add a test for it. While at it, I noticed that `git hook list -h` runs twice in the `git hook usage` test, so remove one invocation. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Replace the bare `char *command` util pointer stored in each string_list item with a heap-allocated `struct hook_config_cache_entry` that carries that command string. This is just a refactoring with no behavior changes, to give the cache entry room to grow, so it can carry the additional hook metadata we'll be adding in the following commits. Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Users running "git hook list" can see which hooks are configured but have no way to tell at which config scope (local, global, system...) each hook was defined. Store the scope from ctx->kvi->scope in the single-pass config callback, then carry it through the cache to the hook structs, so we can expose it to users via the "git hook list --show-scope" flag, which mirrors the existing git config --show-scope convention. Without the flag the output is unchanged. The scope is printed as a tab-separated prefix (like "git config --show-scope"), making it unambiguously machine-parseable even when the friendly name contains spaces. Example usage: $ git hook list --show-scope pre-commit global linter local no-leaks hook from hookdir Traditional hooks from the hookdir are unaffected by --show-scope since the config scope concept does not apply to them. Suggested-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Disabled hooks were filtered out of the cache entirely, making them invisible to "git hook list". Keep them in the cache with a new "disabled" flag which is propagated to the respective struct hook. "git hook list" now shows disabled hooks as tab-separated columns, with the status as a prefix before the name (like scope with --show-scope). With --show-scope it looks like: $ git hook list --show-scope pre-commit global linter local disabled no-leaks hook from hookdir A disabled hook without a command issues a warning instead of the fatal "hook.X.command must be configured" error. We could also throw an error, however it seemd a bit excessive to me in this case. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Teach "git hook run" and "git hook list" to reject hook event names that are not recognized by Git. This helps catch typos such as "prereceive" when "pre-receive" was intended, since in 99% of the cases users want known (already-existing) hook names. The list of known hooks is derived from the generated hook-list.h (built from Documentation/githooks.adoc). This is why the Makefile is updated, so builtin/hook.c depends on hook-list.h. In meson the header is already a dependency for all builtins, no change required. The "--allow-unknown-hook-name" flag can be used to bypass this check. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
The logic for formatting revert commit messages (handling "Revert" and
"Reapply" cases, appending "This reverts commit <ref>.", and handling
merge-parent references) currently lives inline in do_pick_commit().
The upcoming replay --revert mode needs to reuse this logic.
Extract all of this into a new sequencer_format_revert_message()
function. The function takes a repository, the subject line, commit,
parent, a use_commit_reference flag, and the output strbuf. It handles
both regular reverts ("Revert "<subject>"") and revert-of-revert cases
("Reapply "<subject>""), and uses refer_to_commit() internally to
format the commit reference.
Update refer_to_commit() to take a struct repository parameter instead
of relying on the_repository, and a bool instead of reading from
replay_opts directly. This makes it usable from the new shared function
without pulling in sequencer-specific state.
Signed-off-by: Siddharth Asthana <siddharthasthana31@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a `--revert <branch>` mode to git replay that undoes the changes introduced by the specified commits. Like --onto and --advance, --revert is a standalone mode: it takes a branch argument and updates that branch with the newly created revert commits. At GitLab, we need this in Gitaly for reverting commits directly on bare repositories without requiring a working tree checkout. The approach is the same as sequencer.c's do_pick_commit() -- cherry-pick and revert are just the same three-way merge with swapped arguments: - Cherry-pick: merge(ancestor=parent, ours=current, theirs=commit) - Revert: merge(ancestor=commit, ours=current, theirs=parent) We swap the base and pickme trees passed to merge_incore_nonrecursive() to reverse the diff direction. Reverts are processed newest-first (matching git revert behavior) to reduce conflicts by peeling off changes from the top. Each revert builds on the result of the previous one via the last_commit fallback in the main replay loop, rather than relying on the parent-mapping used for cherry-pick. Revert commit messages follow the usual git revert conventions: prefixed with "Revert" (or "Reapply" when reverting a revert), and including "This reverts commit <hash>.". The author is set to the current user rather than preserving the original author, matching git revert behavior. Helped-by: Christian Couder <christian.couder@gmail.com> Helped-by: Patrick Steinhardt <ps@pks.im> Helped-by: Elijah Newren <newren@gmail.com> Helped-by: Phillip Wood <phillip.wood123@gmail.com> Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Helped-by: Junio C Hamano <gitster@pobox.com> Helped-by: Toon Claes <toon@iotcl.com> Signed-off-by: Siddharth Asthana <siddharthasthana31@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* sa/replay-revert: replay: add --revert mode to reverse commit changes sequencer: extract revert message formatting into shared function
Recently some GitHub CI jobs were broken by update on the platform side, which was eventually resolved by image rollback, but in the meantime Dscho invented a workaround patch to sidestep the broken part of the platform. Their future image update may contain the same bug, in which case the workaround may again become needed. As we do not want to be building with workaround that avoids system regexp library altogether unless the system is known to be broken, so short of an automated "detect broken system and apply workaround" mechanism, let's use the folks who are compiling the code to detect breakage on their system and cope with the breakage ;-) Signed-off-by: Junio C Hamano <gitster@pobox.com>
Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5. - [Release notes](https://github.com/actions/cache/releases) - [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md) - [Commits](actions/cache@v4...v5) updated-dependencies: - dependency-name: actions/cache dependency-version: '5' dependency-type: direct:production update-type: version-update:semver-major Originally-authored-by: dependabot[bot] <support@github.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Translate 198 previously fuzzy or untranslated messages, bringing the total number of translated messages to 6226. Reviewed-by: 依云 <lilydjwg@gmail.com> Reviewed-by: Fangyi Zhou <me@fangyi.io> Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
- correct translation of pathspec msgs Corrects cases where the “pathspec” is translated as if it was a path - correct translation of refspec msgs Corrects cases where the “refspec” were not consistently translated - correct translation of credential msgs Corrects cases where the “credential” were not correctly translated Signed-off-by: Stefan Björnelund <stefan.bjornelund.gnome@gmail.com> Modified-by: Peter Krefting <peter@softwolves.pp.se>
Signed-off-by: Peter Krefting <peter@softwolves.pp.se>
We introduced midx version 2 in b2ec8e9 (midx: do not require packs to be sorted in lexicographic order, 2026-02-24) and now write it by default. The rationale was that older versions should ignore the v2 midx and fall back to using the packs (just like we do for other midx errors). Unfortunately this is not the case, as we have a hard die() when we see an unknown midx version. As a result, writing a midx with Git 2.54-rc2 puts the repository into a state that is unusable with Git 2.53. And this midx write may happen behind the scenes as part of normal operations, like fetch. Let's switch back to writing v1 by default to avoid regressing the case where multiple versions of Git are used on the same repository. There is one gotcha, though: the v2 format is required for some new features, like midx compaction, and running "git multi-pack-index compact" will complain when asked to write a v1 index. The user must set midx.version to "2" to make the feature work. So instead of always using v1, we'll base the default on whether the requested feature requires v2. That does mean that running midx compaction will create a repository that can't be read by older versions of Git. But we never do that by default; only people experimenting with the new feature will be affected. We have to adjust the test expectation in t5319, since it will now generate v1 files. And our "auto-select v2" is covered by the tests in t5335, which continue to check that compaction works without having to set midx.version manually (and also explicitly check that asking for v1 with compaction reports the problem). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
As writing version 2 MIDX files by default breaks older versions of Git and its reimplementations, use V2 only when necessary. * jk/midx-write-v1-by-default: MIDX: revert the default version to v1
Signed-off-by: Emir SARI <emir_sari@icloud.com>
Fix various issues in the release notes -- missing/wrong articles, typo, indentation, quote consistency, and wording improvement or corrections. Other than the indentation fix for "The way combined list-object filter options...", this patch is much easier to view with --color-words. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
a8215a2 (send-email: add client certificate options, 2026-03-02) added documentation for sendemail.smtpSSLClientKey that says it works "in conjunction with `sendemail.smtpSSLClientKey`" -- referring to itself. It appears that `sendemail.smtpSSLClientCert` was the intended reference; fix it. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
hierarchies -> hierarchy Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
conflict -> conflicts Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
6cc6d1b (Documentation: update add --force option + ignore=all config, 2026-02-06) added text describing both the ignore=none and ignore=all behaviors. The former had minor formatting and grammatical errors, while the latter was a bit garbled. I have tried to tweak the wording on the latter to make it read as I think was intended, and fixed the minor grammatical issues with both as well. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
* 'zh_CN-2.54' of github.com:jiangxin/git: l10n: zh_CN: updated translation for 2.54
* 'tr-l10n' of github.com:bitigchi/git-po: l10n: tr: Update Turkish translations
* 'apply-patch-reject' of github.com:A4-Tacks/git-po: l10n: fix 'zh_TW.po' 'Applying patch'
* 'master' of github.com:nafmo/git-l10n-sv: l10n: sv.po: Update Swedish translation l10n: sv.po: correct various translations
Signed-off-by: Aindriú Mac Giolla Eoin <aindriu80@gmail.com>
Signed-off-by: Mikel Forcada <mikel.forcada@gmail.com> Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
* 'master' of github.com:alshopov/git-po: l10n: bg.po: Updated Bulgarian translation (6226t)
* 'fr_v2.54.0' of github.com:jnavila/git: l10n: fr: v2.54.0
Signed-off-by: Yi-Jyun Pan <pan93412@gmail.com>
Improvements prompted by AI-assisted review Signed-off-by: Alexander Shopov <ash@kambanaria.org>
* 'master' of github.com:alshopov/git-po: l10n: bg.po: Updated Bulgarian translation (6226t)
l10n-2.54.0-v2 * tag 'l10n-2.54.0-v2' of https://github.com/git-l10n/git-po: l10n: bg.po: Updated Bulgarian translation (6226t) l10n: zh_TW: update translation for Git 2.54 l10n: Update Catalan Translation l10n: ga.po: update for Git 2.54 l10n: fr: v2.54.0 l10n: tr: Update Turkish translations l10n: sv.po: Update Swedish translation l10n: sv.po: correct various translations l10n: zh_CN: updated translation for 2.54 l10n: bg.po: Updated Bulgarian translation (6226t) l10n: zh_CN: post-2.53 code review l10n: document AI and PO helper in po/README l10n: docs: add review instructions in AGENTS.md l10n: docs: add translation instructions in AGENTS.md l10n: docs: add update PO instructions in AGENTS.md l10n: docs: add AGENTS.md with update POT instructions l10n: add .gitattributes to simplify location filtering l10n: fix 'zh_TW.po' 'Applying patch'
Git diff is about comparing two endpoints. Pass endpoints as determined by diff argument parsing to external tools via environment variables. External tools receive a path and the contents to compare in temporary files. Tools are unable to display the commits being compared, nor the paths if one was renamed. A common scenario is a GUI client invoking an external tool via difftool. The GUI client knows the selected commits, but few if any clients pass that information to the external tool. Git receives the commits to compare, and is in a position to share the endpoints with the external tool. External tools should be able to display endpoints that enable users to locate the content being compared, ideally in terms of commit objects and paths. Address this problem by exporting the following variables: GIT_DIFF_ENDPOINT_A GIT_DIFF_ENDPOINT_B GIT_DIFF_PATH_A GIT_DIFF_PATH_B The ENDPOINT_* variables are the endpoints as determined by the builtin diff argument parsing. Ideally the values are object ids for commits, but will degrade to tree objects if the arguments are trees. A PATH_* variable is the path of the contents in the corresponding endpoint. For clarity, both variables are set even if the paths are the same. When a blob is added or deleted, the other path is /dev/null. If --relative is specified, the paths are relative. Out of scope: - diffs vs the index, working tree, or no-index: these could be handled in the future by indicating the endpoint is 'index', 'working-tree' or 'no-index'. - merge-commits: the current approach does not consider how to handle more than two endpoints. Environment variables will not be set. - GIT_EXTERNAL_DIFF does not support --submodule=diff, and therefore is not considered at this time. - difftool --dir-diff invokes the external tool on two directories. This is achieved by invoking diff to find the differences. This prevents environment variables from being passed back to difftool.
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Git diff is about comparing two endpoints. Pass endpoints as determined by diff argument parsing to external tools via environment variables.
External tools receive a path and the contents to compare in temporary files. Tools are unable to display the commits being compared, nor the paths if one was renamed. A common scenario is a GUI client invoking an external tool via difftool. The GUI client knows the selected commits, but few if any clients pass that information to the external tool. Git receives the commits to compare, and is in a position to share the endpoints with the external tool.
External tools should be able to display endpoints that enable users to locate the content being compared, ideally in terms of commit objects and paths.
Address this problem by exporting the following variables:
GIT_DIFF_ENDPOINT_A
GIT_DIFF_ENDPOINT_B
GIT_DIFF_PATH_A
GIT_DIFF_PATH_B
The ENDPOINT_* variables are the endpoints as determined by the builtin diff argument parsing. Ideally the values are object ids for commits, but will degrade to tree objects if the arguments are trees.
A PATH_* variable is the path of the contents in the corresponding endpoint. For clarity, both variables are set even if the paths are the same. When a blob is added or deleted, the other path is /dev/null.
If --relative is specified, the paths are relative.
Out of scope:
diffs vs the index, working tree, or no-index: these could be handled in the future by indicating the endpoint is 'index', 'working-tree' or 'no-index'.
merge-commits: the current approach does not consider how to handle more than two endpoints. Environment variables will not be set.
GIT_EXTERNAL_DIFF does not support --submodule=diff, and therefore is not considered at this time.
difftool --dir-diff invokes the external tool on two directories. This is achieved by invoking diff to find the differences. This prevents environment variables from being passed back to difftool.