revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/ll-merge.h

@@ -7,87 +7,16 @@
 
 #include "xdiff/xdiff.h"
 
-/**
- *
- * Calling sequence:
- * ----------------
- *
- * - Prepare a `struct ll_merge_options` to record options.
- *   If you have no special requests, skip this and pass `NULL`
- *   as the `opts` parameter to use the default options.
- *
- * - Allocate an mmbuffer_t variable for the result.
- *
- * - Allocate and fill variables with the file's original content
- *   and two modified versions (using `read_mmfile`, for example).
- *
- * - Call `ll_merge()`.
- *
- * - Read the merged content from `result_buf.ptr` and `result_buf.size`.
- *
- * - Release buffers when finished.  A simple
- *   `free(ancestor.ptr); free(ours.ptr); free(theirs.ptr);
- *   free(result_buf.ptr);` will do.
- *
- * If the modifications do not merge cleanly, `ll_merge` will return a
- * nonzero value and `result_buf` will generally include a description of
- * the conflict bracketed by markers such as the traditional `<<<<<<<`
- * and `>>>>>>>`.
- *
- * The `ancestor_label`, `our_label`, and `their_label` parameters are
- * used to label the different sides of a conflict if the merge driver
- * supports this.
- */
-
-
 struct index_state;
 
-/**
- * This describes the set of options the calling program wants to affect
- * the operation of a low-level (single file) merge.
- */
 struct ll_merge_options {
-
-	/**
-	 * Behave as though this were part of a merge between common ancestors in
-	 * a recursive merge (merges of binary files may need to be handled
-	 * differently in such cases, for example). If a helper program is
-	 * specified by the `[merge "<driver>"] recursive` configuration, it will
-	 * be used.
-	 */
 	unsigned virtual_ancestor : 1;
-
-	/**
-	 * Resolve local conflicts automatically in favor of one side or the other
-	 * (as in 'git merge-file' `--ours`/`--theirs`/`--union`).  Can be `0`,
-	 * `XDL_MERGE_FAVOR_OURS`, `XDL_MERGE_FAVOR_THEIRS`,
-	 * or `XDL_MERGE_FAVOR_UNION`.
-	 */
-	unsigned variant : 2;
-
-	/**
-	 * Resmudge and clean the "base", "theirs" and "ours" files before merging.
-	 * Use this when the merge is likely to have overlapped with a change in
-	 * smudge/clean or end-of-line normalization rules.
-	 */
+	unsigned variant : 2;	/* favor ours, favor theirs, or union merge */
 	unsigned renormalize : 1;
-
-	/**
-	 * Increase the length of conflict markers so that nested conflicts
-	 * can be differentiated.
-	 */
 	unsigned extra_marker_size;
-
-	/* Extra xpparam_t flags as defined in xdiff/xdiff.h. */
 	long xdl_opts;
 };
 
-/**
- * Perform a three-way single-file merge in core.  This is a thin wrapper
- * around `xdl_merge` that takes the path and any merge backend specified in
- * `.gitattributes` or `.git/info/attributes` into account.
- * Returns 0 for a clean merge.
- */
 int ll_merge(mmbuffer_t *result_buf,
 	     const char *path,
 	     mmfile_t *ancestor, const char *ancestor_label,
@@ -97,6 +26,5 @@ int ll_merge(mmbuffer_t *result_buf,
 	     const struct ll_merge_options *opts);
 
 int ll_merge_marker_size(struct index_state *istate, const char *path);
-void reset_merge_attributes(void);
 
 #endif