Merge branch 'ab/pickaxe-pcre2'

Rewrite the backend for "diff -G/-S" to use pcre2 engine when
available.

* ab/pickaxe-pcre2: (22 commits)
  xdiff-interface: replace discard_hunk_line() with a flag
  xdiff users: use designated initializers for out_line
  pickaxe -G: don't special-case create/delete
  pickaxe -G: terminate early on matching lines
  xdiff-interface: allow early return from xdiff_emit_line_fn
  xdiff-interface: prepare for allowing early return
  pickaxe -S: slightly optimize contains()
  pickaxe: rename variables in has_changes() for brevity
  pickaxe -S: support content with NULs under --pickaxe-regex
  pickaxe: assert that we must have a needle under -G or -S
  pickaxe: refactor function selection in diffcore-pickaxe()
  perf: add performance test for pickaxe
  pickaxe/style: consolidate declarations and assignments
  diff.h: move pickaxe fields together again
  pickaxe: die when --find-object and --pickaxe-all are combined
  pickaxe: die when -G and --pickaxe-regex are combined
  pickaxe tests: add missing test for --no-pickaxe-regex being an error
  pickaxe tests: test for -G, -S and --find-object incompatibility
  pickaxe tests: add test for "log -S" not being a regex
  pickaxe tests: add test for diffgrep_consume() internals
  ...

1 files changed, 22 insertions, 9 deletions

diff --git a/xdiff-interface.h b/xdiff-interface.h
index 93df26900c..4301a7eef2 100644
--- a/xdiff-interface.h
+++ b/xdiff-interface.h
@@ -11,7 +11,28 @@
  */
 #define MAX_XDIFF_SIZE (1024UL * 1024 * 1023)
 
-typedef void (*xdiff_emit_line_fn)(void *, char *, unsigned long);
+/**
+ * The `xdiff_emit_line_fn` function can return 1 to abort early, or 0
+ * to continue processing. Note that doing so is an all-or-nothing
+ * affair, as returning 1 will return all the way to the top-level,
+ * e.g. the xdi_diff_outf() call to generate the diff.
+ *
+ * Thus returning 1 means you won't be getting any more diff lines. If
+ * you need something in-between those two options you'll to use
+ * `xdl_emit_hunk_consume_func_t` and implement your own version of
+ * xdl_emit_diff().
+ *
+ * We may extend the interface in the future to understand other more
+ * granular return values. While you should return 1 to exit early,
+ * doing so will currently make your early return indistinguishable
+ * from an error internal to xdiff, xdiff itself will see that
+ * non-zero return and translate it to -1.
+ *
+ * See "diff_grep" in diffcore-pickaxe.c for a trick to work around
+ * this, i.e. using the "consume_callback_data" to note the desired
+ * early return.
+ */
+typedef int (*xdiff_emit_line_fn)(void *, char *, unsigned long);
 typedef void (*xdiff_emit_hunk_fn)(void *data,
 				   long old_begin, long old_nr,
 				   long new_begin, long new_nr,
@@ -33,14 +54,6 @@ int git_xmerge_config(const char *var, const char *value, void *cb);
 extern int git_xmerge_style;
 
 /*
- * Can be used as a no-op hunk_fn for xdi_diff_outf(), since a NULL
- * one just sends the hunk line to the line_fn callback).
- */
-void discard_hunk_line(void *priv,
-		       long ob, long on, long nb, long nn,
-		       const char *func, long funclen);
-
-/*
  * Compare the strings l1 with l2 which are of size s1 and s2 respectively.
  * Returns 1 if the strings are deemed equal, 0 otherwise.
  * The `flags` given as XDF_WHITESPACE_FLAGS determine how white spaces