1 files changed, 379 insertions, 0 deletions
diff --git a/ll-merge.c b/ll-merge.c
new file mode 100644
index 0000000000..5ae74331bc
--- /dev/null
+++ b/ll-merge.c
@@ -0,0 +1,379 @@
+/*
+ * Low level 3-way in-core file merge.
+ *
+ * Copyright (c) 2007 Junio C Hamano
+ */
+
+#include "cache.h"
+#include "attr.h"
+#include "xdiff-interface.h"
+#include "run-command.h"
+#include "interpolate.h"
+#include "ll-merge.h"
+
+struct ll_merge_driver;
+
+typedef int (*ll_merge_fn)(const struct ll_merge_driver *,
+			   mmbuffer_t *result,
+			   const char *path,
+			   mmfile_t *orig,
+			   mmfile_t *src1, const char *name1,
+			   mmfile_t *src2, const char *name2,
+			   int virtual_ancestor);
+
+struct ll_merge_driver {
+	const char *name;
+	const char *description;
+	ll_merge_fn fn;
+	const char *recursive;
+	struct ll_merge_driver *next;
+	char *cmdline;
+};
+
+/*
+ * Built-in low-levels
+ */
+static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
+			   mmbuffer_t *result,
+			   const char *path_unused,
+			   mmfile_t *orig,
+			   mmfile_t *src1, const char *name1,
+			   mmfile_t *src2, const char *name2,
+			   int virtual_ancestor)
+{
+	/*
+	 * The tentative merge result is "ours" for the final round,
+	 * or common ancestor for an internal merge.  Still return
+	 * "conflicted merge" status.
+	 */
+	mmfile_t *stolen = virtual_ancestor ? orig : src1;
+
+	result->ptr = stolen->ptr;
+	result->size = stolen->size;
+	stolen->ptr = NULL;
+	return 1;
+}
+
+static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
+			mmbuffer_t *result,
+			const char *path_unused,
+			mmfile_t *orig,
+			mmfile_t *src1, const char *name1,
+			mmfile_t *src2, const char *name2,
+			int virtual_ancestor)
+{
+	xpparam_t xpp;
+
+	if (buffer_is_binary(orig->ptr, orig->size) ||
+	    buffer_is_binary(src1->ptr, src1->size) ||
+	    buffer_is_binary(src2->ptr, src2->size)) {
+		warning("Cannot merge binary files: %s vs. %s\n",
+			name1, name2);
+		return ll_binary_merge(drv_unused, result,
+				       path_unused,
+				       orig, src1, name1,
+				       src2, name2,
+				       virtual_ancestor);
+	}
+
+	memset(&xpp, 0, sizeof(xpp));
+	return xdl_merge(orig,
+			 src1, name1,
+			 src2, name2,
+			 &xpp, XDL_MERGE_ZEALOUS,
+			 result);
+}
+
+static int ll_union_merge(const struct ll_merge_driver *drv_unused,
+			  mmbuffer_t *result,
+			  const char *path_unused,
+			  mmfile_t *orig,
+			  mmfile_t *src1, const char *name1,
+			  mmfile_t *src2, const char *name2,
+			  int virtual_ancestor)
+{
+	char *src, *dst;
+	long size;
+	const int marker_size = 7;
+
+	int status = ll_xdl_merge(drv_unused, result, path_unused,
+				  orig, src1, NULL, src2, NULL,
+				  virtual_ancestor);
+	if (status <= 0)
+		return status;
+	size = result->size;
+	src = dst = result->ptr;
+	while (size) {
+		char ch;
+		if ((marker_size < size) &&
+		    (*src == '<' || *src == '=' || *src == '>')) {
+			int i;
+			ch = *src;
+			for (i = 0; i < marker_size; i++)
+				if (src[i] != ch)
+					goto not_a_marker;
+			if (src[marker_size] != '\n')
+				goto not_a_marker;
+			src += marker_size + 1;
+			size -= marker_size + 1;
+			continue;
+		}
+	not_a_marker:
+		do {
+			ch = *src++;
+			*dst++ = ch;
+			size--;
+		} while (ch != '\n' && size);
+	}
+	result->size = dst - result->ptr;
+	return 0;
+}
+
+#define LL_BINARY_MERGE 0
+#define LL_TEXT_MERGE 1
+#define LL_UNION_MERGE 2
+static struct ll_merge_driver ll_merge_drv[] = {
+	{ "binary", "built-in binary merge", ll_binary_merge },
+	{ "text", "built-in 3-way text merge", ll_xdl_merge },
+	{ "union", "built-in union merge", ll_union_merge },
+};
+
+static void create_temp(mmfile_t *src, char *path)
+{
+	int fd;
+
+	strcpy(path, ".merge_file_XXXXXX");
+	fd = xmkstemp(path);
+	if (write_in_full(fd, src->ptr, src->size) != src->size)
+		die("unable to write temp-file");
+	close(fd);
+}
+
+/*
+ * User defined low-level merge driver support.
+ */
+static int ll_ext_merge(const struct ll_merge_driver *fn,
+			mmbuffer_t *result,
+			const char *path,
+			mmfile_t *orig,
+			mmfile_t *src1, const char *name1,
+			mmfile_t *src2, const char *name2,
+			int virtual_ancestor)
+{
+	char temp[3][50];
+	char cmdbuf[2048];
+	struct interp table[] = {
+		{ "%O" },
+		{ "%A" },
+		{ "%B" },
+	};
+	struct child_process child;
+	const char *args[20];
+	int status, fd, i;
+	struct stat st;
+
+	if (fn->cmdline == NULL)
+		die("custom merge driver %s lacks command line.", fn->name);
+
+	result->ptr = NULL;
+	result->size = 0;
+	create_temp(orig, temp[0]);
+	create_temp(src1, temp[1]);
+	create_temp(src2, temp[2]);
+
+	interp_set_entry(table, 0, temp[0]);
+	interp_set_entry(table, 1, temp[1]);
+	interp_set_entry(table, 2, temp[2]);
+
+	interpolate(cmdbuf, sizeof(cmdbuf), fn->cmdline, table, 3);
+
+	memset(&child, 0, sizeof(child));
+	child.argv = args;
+	args[0] = "sh";
+	args[1] = "-c";
+	args[2] = cmdbuf;
+	args[3] = NULL;
+
+	status = run_command(&child);
+	if (status < -ERR_RUN_COMMAND_FORK)
+		; /* failure in run-command */
+	else
+		status = -status;
+	fd = open(temp[1], O_RDONLY);
+	if (fd < 0)
+		goto bad;
+	if (fstat(fd, &st))
+		goto close_bad;
+	result->size = st.st_size;
+	result->ptr = xmalloc(result->size + 1);
+	if (read_in_full(fd, result->ptr, result->size) != result->size) {
+		free(result->ptr);
+		result->ptr = NULL;
+		result->size = 0;
+	}
+ close_bad:
+	close(fd);
+ bad:
+	for (i = 0; i < 3; i++)
+		unlink(temp[i]);
+	return status;
+}
+
+/*
+ * merge.default and merge.driver configuration items
+ */
+static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
+static const char *default_ll_merge;
+
+static int read_merge_config(const char *var, const char *value)
+{
+	struct ll_merge_driver *fn;
+	const char *ep, *name;
+	int namelen;
+
+	if (!strcmp(var, "merge.default")) {
+		if (value)
+			default_ll_merge = strdup(value);
+		return 0;
+	}
+
+	/*
+	 * We are not interested in anything but "merge.<name>.variable";
+	 * especially, we do not want to look at variables such as
+	 * "merge.summary", "merge.tool", and "merge.verbosity".
+	 */
+	if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
+		return 0;
+
+	/*
+	 * Find existing one as we might be processing merge.<name>.var2
+	 * after seeing merge.<name>.var1.
+	 */
+	name = var + 6;
+	namelen = ep - name;
+	for (fn = ll_user_merge; fn; fn = fn->next)
+		if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
+			break;
+	if (!fn) {
+		fn = xcalloc(1, sizeof(struct ll_merge_driver));
+		fn->name = xmemdupz(name, namelen);
+		fn->fn = ll_ext_merge;
+		*ll_user_merge_tail = fn;
+		ll_user_merge_tail = &(fn->next);
+	}
+
+	ep++;
+
+	if (!strcmp("name", ep)) {
+		if (!value)
+			return error("%s: lacks value", var);
+		fn->description = strdup(value);
+		return 0;
+	}
+
+	if (!strcmp("driver", ep)) {
+		if (!value)
+			return error("%s: lacks value", var);
+		/*
+		 * merge.<name>.driver specifies the command line:
+		 *
+		 *	command-line
+		 *
+		 * The command-line will be interpolated with the following
+		 * tokens and is given to the shell:
+		 *
+		 *    %O - temporary file name for the merge base.
+		 *    %A - temporary file name for our version.
+		 *    %B - temporary file name for the other branches' version.
+		 *
+		 * The external merge driver should write the results in the
+		 * file named by %A, and signal that it has done with zero exit
+		 * status.
+		 */
+		fn->cmdline = strdup(value);
+		return 0;
+	}
+
+	if (!strcmp("recursive", ep)) {
+		if (!value)
+			return error("%s: lacks value", var);
+		fn->recursive = strdup(value);
+		return 0;
+	}
+
+	return 0;
+}
+
+static void initialize_ll_merge(void)
+{
+	if (ll_user_merge_tail)
+		return;
+	ll_user_merge_tail = &ll_user_merge;
+	git_config(read_merge_config);
+}
+
+static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
+{
+	struct ll_merge_driver *fn;
+	const char *name;
+	int i;
+
+	initialize_ll_merge();
+
+	if (ATTR_TRUE(merge_attr))
+		return &ll_merge_drv[LL_TEXT_MERGE];
+	else if (ATTR_FALSE(merge_attr))
+		return &ll_merge_drv[LL_BINARY_MERGE];
+	else if (ATTR_UNSET(merge_attr)) {
+		if (!default_ll_merge)
+			return &ll_merge_drv[LL_TEXT_MERGE];
+		else
+			name = default_ll_merge;
+	}
+	else
+		name = merge_attr;
+
+	for (fn = ll_user_merge; fn; fn = fn->next)
+		if (!strcmp(fn->name, name))
+			return fn;
+
+	for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
+		if (!strcmp(ll_merge_drv[i].name, name))
+			return &ll_merge_drv[i];
+
+	/* default to the 3-way */
+	return &ll_merge_drv[LL_TEXT_MERGE];
+}
+
+static const char *git_path_check_merge(const char *path)
+{
+	static struct git_attr_check attr_merge_check;
+
+	if (!attr_merge_check.attr)
+		attr_merge_check.attr = git_attr("merge", 5);
+
+	if (git_checkattr(path, 1, &attr_merge_check))
+		return NULL;
+	return attr_merge_check.value;
+}
+
+int ll_merge(mmbuffer_t *result_buf,
+	     const char *path,
+	     mmfile_t *ancestor,
+	     mmfile_t *ours, const char *our_label,
+	     mmfile_t *theirs, const char *their_label,
+	     int virtual_ancestor)
+{
+	const char *ll_driver_name;
+	const struct ll_merge_driver *driver;
+
+	ll_driver_name = git_path_check_merge(path);
+	driver = find_ll_merge_driver(ll_driver_name);
+
+	if (virtual_ancestor && driver->recursive)
+		driver = find_ll_merge_driver(driver->recursive);
+	return driver->fn(driver, result_buf, path,
+			  ancestor,
+			  ours, our_label,
+			  theirs, their_label, virtual_ancestor);
+}