fast-import: Hide the pack boundary commits by default.

Most users don't need the pack boundary information that fast-import
was printing to standard output, especially if they were calling
it with --quiet.

Those users who do want this information probably want it captured
so they can go back and use it to repack the imported repository.
So dumping the boundary commits to a log file makes more sense then
printing them to standard output.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

Documentation/git-fast-import.txt

@@ -64,6 +64,15 @@ OPTIONS
 	Frontends can use this file to validate imports after they
 	have been completed.
 
+--export-pack-edges=<file>::
+	After creating a packfile, print a line of data to
+	<file> listing the filename of the packfile and the last
+	commit on each branch that was written to that packfile.
+	This information may be useful after importing projects
+	whose total object set exceeds the 4 GiB packfile limit,
+	as these commits can be used as edge points during calls
+	to gitlink:git-pack-objects[1].
+
 --quiet::
 	Disable all non-fatal output, making fast-import silent when it
 	is successful.	This option disables the output shown by

fast-import.c

@@ -261,6 +261,7 @@ static unsigned long object_count;
 static unsigned long branch_count;
 static unsigned long branch_load_count;
 static int failure;
+static FILE *pack_edges;
 
 /* Memory pools */
 static size_t mem_pool_alloc = 2*1024*1024 - sizeof(struct mem_pool);
@@ -811,18 +812,21 @@ static void end_packfile(void)
 		install_packed_git(new_p);
 
 		/* Print the boundary */
-		fprintf(stdout, "%s:", new_p->pack_name);
-		for (i = 0; i < branch_table_sz; i++) {
-			for (b = branch_table[i]; b; b = b->table_next_branch) {
-				if (b->pack_id == pack_id)
-					fprintf(stdout, " %s", sha1_to_hex(b->sha1));
+		if (pack_edges) {
+			fprintf(pack_edges, "%s:", new_p->pack_name);
+			for (i = 0; i < branch_table_sz; i++) {
+				for (b = branch_table[i]; b; b = b->table_next_branch) {
+					if (b->pack_id == pack_id)
+						fprintf(pack_edges, " %s", sha1_to_hex(b->sha1));
+				}
 			}
+			for (t = first_tag; t; t = t->next_tag) {
+				if (t->pack_id == pack_id)
+					fprintf(pack_edges, " %s", sha1_to_hex(t->sha1));
+			}
+			fputc('\n', pack_edges);
+			fflush(pack_edges);
 		}
-		for (t = first_tag; t; t = t->next_tag) {
-			if (t->pack_id == pack_id)
-				fprintf(stdout, " %s", sha1_to_hex(t->sha1));
-		}
-		fputc('\n', stdout);
 
 		pack_id++;
 	}
@@ -1988,7 +1992,13 @@ int main(int argc, const char **argv)
 			max_active_branches = strtoul(a + 18, NULL, 0);
 		else if (!strncmp(a, "--export-marks=", 15))
 			mark_file = a + 15;
-		else if (!strcmp(a, "--force"))
+		else if (!strncmp(a, "--export-pack-edges=", 20)) {
+			if (pack_edges)
+				fclose(pack_edges);
+			pack_edges = fopen(a + 20, "a");
+			if (!pack_edges)
+				die("Cannot open %s: %s", a + 20, strerror(errno));
+		} else if (!strcmp(a, "--force"))
 			force_update = 1;
 		else if (!strcmp(a, "--quiet"))
 			show_stats = 0;
@@ -2033,6 +2043,9 @@ int main(int argc, const char **argv)
 	unkeep_all_packs();
 	dump_marks();
 
+	if (pack_edges)
+		fclose(pack_edges);
+
 	if (show_stats) {
 		uintmax_t total_count = 0, duplicate_count = 0;
 		for (i = 0; i < ARRAY_SIZE(object_count_by_type); i++)

t/t9300-fast-import.sh

@@ -407,4 +407,30 @@ test_expect_success \
 	'git-cat-file blob H:h/e/l/lo >actual &&
 	 diff -u expect actual'
 
+###
+### series I
+###
+
+cat >input <<INPUT_END
+commit refs/heads/export-boundary
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+we have a border.  its only 40 characters wide.
+COMMIT
+
+from refs/heads/branch
+
+INPUT_END
+test_expect_success \
+    'I: export-pack-edges' \
+    'git-fast-import --export-pack-edges=edges.list <input'
+
+cat >expect <<EOF
+.git/objects/pack/pack-.pack: `git-rev-parse --verify export-boundary`
+EOF
+test_expect_success \
+	'I: verify edge list' \
+	'sed -e s/pack-.*pack/pack-.pack/ edges.list >actual &&
+	 diff -u expect actual'
+
 test_done