[PATCH v2 03/20] merge-ort: port merge_start() from merge-recursive

From: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date: Dec 4, 2020, 20:47 UTC
Message-ID: <acb40f5c165fa6dd2fe54caee3bcb4f2b24507e3.1607114890.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.923.v2.git.git.1607114890.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

merge_start() basically does a bunch of sanity checks, then allocates and initializes opt->priv -- a struct merge_options_internal.

Most of the sanity checks are usable as-is. The allocation/intialization is a bit different since merge-ort has a very different merge_options_internal than merge-recursive, but the idea is the same.

The weirdest part here is that merge-ort and merge-recursive use the
same struct merge_options, even though merge_options has a number of
fields that are oddly specific to merge-recursive's internal
implementation and don't even make sense with merge-ort's high-level
design (e.g. buffer_output, which merge-ort has to always do).  I reused
the same data structure because:
  * most the fields made sense to both merge algorithms
  * making a new struct would have required making new enums or somehow
    externalizing them, and that was getting messy.
  * it simplifies converting the existing callers by not having to
    have different code paths for merge_options setup.

I also marked detect_renames as ignored. We can revisit that later, but in short: merge-recursive allowed turning off rename detection because it was sometimes glacially slow. When you speed something up by a few orders of magnitude, it's worth revisiting whether that justification is still relevant. Besides, if folks find it's still too slow, perhaps they have a better scaling case than I could find and maybe it turns up some more optimizations we can add. If it still is needed as an option, it is easy to add later.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 merge-ort.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/merge-ort.c b/merge-ort.c
index 8c9fea1a5a..f8ac721aa3 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -17,6 +17,8 @@
 #include "cache.h"
 #include "merge-ort.h"
 
+#include "diff.h"
+#include "diffcore.h"
 #include "strmap.h"
 #include "tree.h"
 
@@ -205,7 +207,48 @@ void merge_finalize(struct merge_options *opt,
 
 static void merge_start(struct merge_options *opt, struct merge_result *result)
 {
-	die("Not yet implemented.");
+	/* Sanity checks on opt */
+	assert(opt->repo);
+
+	assert(opt->branch1 && opt->branch2);
+
+	assert(opt->detect_directory_renames >= MERGE_DIRECTORY_RENAMES_NONE &&
+	       opt->detect_directory_renames <= MERGE_DIRECTORY_RENAMES_TRUE);
+	assert(opt->rename_limit >= -1);
+	assert(opt->rename_score >= 0 && opt->rename_score <= MAX_SCORE);
+	assert(opt->show_rename_progress >= 0 && opt->show_rename_progress <= 1);
+
+	assert(opt->xdl_opts >= 0);
+	assert(opt->recursive_variant >= MERGE_VARIANT_NORMAL &&
+	       opt->recursive_variant <= MERGE_VARIANT_THEIRS);
+
+	/*
+	 * detect_renames, verbosity, buffer_output, and obuf are ignored
+	 * fields that were used by "recursive" rather than "ort" -- but
+	 * sanity check them anyway.
+	 */
+	assert(opt->detect_renames >= -1 &&
+	       opt->detect_renames <= DIFF_DETECT_COPY);
+	assert(opt->verbosity >= 0 && opt->verbosity <= 5);
+	assert(opt->buffer_output <= 2);
+	assert(opt->obuf.len == 0);
+
+	assert(opt->priv == NULL);
+
+	/* Initialization of opt->priv, our internal merge data */
+	opt->priv = xcalloc(1, sizeof(*opt->priv));
+
+	/*
+	 * Although we initialize opt->priv->paths with strdup_strings=0,
+	 * that's just to avoid making yet another copy of an allocated
+	 * string.  Putting the entry into paths means we are taking
+	 * ownership, so we will later free it.
+	 *
+	 * In contrast, conflicted just has a subset of keys from paths, so
+	 * we don't want to free those (it'd be a duplicate free).
+	 */
+	strmap_init_with_options(&opt->priv->paths, NULL, 0);
+	strmap_init_with_options(&opt->priv->conflicted, NULL, 0);
 }
 
 /*

-- 
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