When a diff process is configured via diff.<driver>.process,
consult it during blame's per-commit diffing. If the process
returns no hunks for a commit's changes to a file, treat the
commit as having no changes, causing blame to attribute lines
to earlier commits.
The consultation happens at the pass_blame_to_parent() callsite
using diff_process_fill_hunks(), matching how builtin_diff() in
diff.c uses the same function. A new diff_hunks_xpp() variant
accepts a pre-populated xpparam_t so callers can pass external
hunks, while the existing diff_hunks() retains its original
signature and behavior. The copy-detection callsite is
unaffected since it does not use the diff process.
The subprocess is long-running (one startup cost amortized
across the blame traversal), but each commit in the file's
history incurs a round-trip to the tool.
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make --no-ext-diff disable diff.<driver>.process in addition to
diff.<driver>.command. Although the two mechanisms work differently
(command replaces Git's output, process feeds hunks back into the
pipeline), both invoke external tools and --no-ext-diff means
"no external tools."
Replace the OPT_BOOL for --ext-diff with an OPT_CALLBACK that
sets both allow_external and no_diff_process, so a single option
controls both. Passing --ext-diff explicitly clears
no_diff_process, so a later --ext-diff overrides an earlier
--no-ext-diff.
Disable the diff process unconditionally in format-patch so that
generated patches are always based on the builtin diff algorithm
and can be applied reliably by recipients who do not have the
external tool.
Document that --diff-algorithm also bypasses the diff process,
since it forces the builtin algorithm.
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add support for external diff processes that communicate via the
long-running process protocol (pkt-line over stdin/stdout).
A diff process is configured per userdiff driver:
[diff "cdiff"]
process = /path/to/diff-tool
The tool provides custom line-matching: it receives file pairs
and returns hunks that reference line numbers in the content.
When textconv is also configured, the tool receives the
textconv-transformed content. The tool controls which lines
are marked as changed while the display shows the file content.
Patch output features (word diff, function context, color) work
normally; --stat uses its own diff codepath and never consults
the diff process.
The handshake negotiates version=1 and capability=hunks. Per-file
requests send command=hunks, pathname, and both file contents as
packetized data. The tool responds with hunk lines and a status
packet (success, error, or abort). On error, Git warns and falls
back to the builtin diff algorithm for that file. On abort, Git
silently falls back for the current file and stops sending further
requests to the tool for the remainder of the session.
When the tool returns no hunks followed by status=success, Git
treats the file as having no changes and produces no diff output.
This also means --exit-code reports no changes for that file.
The subprocess is stored on the userdiff_driver struct and
launched on first use. If the process fails to start, the
handshake fails, or a communication error occurs mid-stream,
the failure is cached on the driver to avoid retrying and
re-warning on every subsequent file.
diff_process_fill_hunks() is the sole public entry point. It
handles driver lookup, flag checks, subprocess management, and
error reporting, returning an enum that lets callers distinguish
"hunks populated" from "files equivalent" from "not applicable"
from "tool failure."
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Michael Montalbo