Add option to disable ctime check for manifest

Make it possible to use e.g. "git-restore-mtime"*,
to use the original timestamps and avoid checksums.

* https://github.com/MestreLion/git-tools

Restoring ctime is much harder than restoring mtime,
since you need to change the system clock to do it.

5 files changed, 30 insertions, 10 deletions

diff --git a/doc/MANUAL.adoc b/doc/MANUAL.adoc
index 9bcc4ede..283e5525 100644
--- a/doc/MANUAL.adoc
+++ b/doc/MANUAL.adoc
@@ -525,6 +525,9 @@ still has to do _some_ preprocessing (like macros).
     ccache normally examines a file's contents to determine whether it matches
     the cached version. With this option set, ccache will consider a file as
     matching its cached version if the mtimes and ctimes match.
+*file_stat_matches_ctime*::
+    By default, ccache will not consider a file as matching its cached
+    version if the ctimes do not match. This option disables that check.
 *include_file_ctime*::
     By default, ccache also will not cache a file if it includes a header whose
     ctime is too new. This option disables that check.
diff --git a/src/ccache.h b/src/ccache.h
index 973d42dd..ff60a582 100644
--- a/src/ccache.h
+++ b/src/ccache.h
@@ -79,6 +79,9 @@ extern enum guessed_compiler guessed_compiler;
 // Allow us to not include any system headers in the manifest include files,
 // similar to -MM versus -M for dependencies.
 #define SLOPPY_NO_SYSTEM_HEADERS 64
+// Allow us to ignore ctimes when comparing file stats, so we can fake mtimes
+// if we want to (it is much harder to fake ctimes, requires changing clock)
+#define SLOPPY_FILE_STAT_MATCHES_CTIME 128
 
 #define str_eq(s1, s2) (strcmp((s1), (s2)) == 0)
 #define str_startswith(s, prefix) \
diff --git a/src/conf.c b/src/conf.c
index dc917092..fa8283fb 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -106,6 +106,8 @@ parse_sloppiness(const char *str, void *result, char **errmsg)
 			*value |= SLOPPY_FILE_MACRO;
 		} else if (str_eq(word, "file_stat_matches")) {
 			*value |= SLOPPY_FILE_STAT_MATCHES;
+		} else if (str_eq(word, "file_stat_matches_ctime")) {
+			*value |= SLOPPY_FILE_STAT_MATCHES_CTIME;
 		} else if (str_eq(word, "include_file_ctime")) {
 			*value |= SLOPPY_INCLUDE_FILE_CTIME;
 		} else if (str_eq(word, "include_file_mtime")) {
@@ -656,6 +658,9 @@ conf_print_items(struct conf *conf,
 	if (conf->sloppiness & SLOPPY_FILE_STAT_MATCHES) {
 		reformat(&s, "%sfile_stat_matches, ", s);
 	}
+	if (conf->sloppiness & SLOPPY_FILE_STAT_MATCHES_CTIME) {
+		reformat(&s, "%sfile_stat_matches_ctime, ", s);
+	}
 	if (conf->sloppiness & SLOPPY_NO_SYSTEM_HEADERS) {
 		reformat(&s, "%sno_system_headers, ", s);
 	}
diff --git a/src/manifest.c b/src/manifest.c
index 1eeccdf9..b2847a08 100644
--- a/src/manifest.c
+++ b/src/manifest.c
@@ -391,11 +391,20 @@ verify_object(struct conf *conf, struct manifest *mf, struct object *obj,
 		}
 
 		if (conf->sloppiness & SLOPPY_FILE_STAT_MATCHES) {
-			if (fi->mtime == st->mtime && fi->ctime == st->ctime) {
-				cc_log("mtime/ctime hit for %s", path);
-				continue;
+			if (!(conf->sloppiness & SLOPPY_FILE_STAT_MATCHES_CTIME)) {
+				if (fi->mtime == st->mtime && fi->ctime == st->ctime) {
+					cc_log("mtime/ctime hit for %s", path);
+					continue;
+				} else {
+					cc_log("mtime/ctime miss for %s", path);
+				}
 			} else {
-				cc_log("mtime/ctime miss for %s", path);
+				if (fi->mtime == st->mtime) {
+					cc_log("mtime hit for %s", path);
+					continue;
+				} else {
+					cc_log("mtime miss for %s", path);
+				}
 			}
 		}
 
diff --git a/unittest/test_conf.c b/unittest/test_conf.c
index 9271a88c..12a193bd 100644
--- a/unittest/test_conf.c
+++ b/unittest/test_conf.c
@@ -128,7 +128,7 @@ TEST(conf_read_valid_config)
 	  "read_only_direct = true\n"
 	  "recache = true\n"
 	  "run_second_cpp = false\n"
-	  "sloppiness =     file_macro   ,time_macros,  include_file_mtime,include_file_ctime,file_stat_matches,pch_defines ,  no_system_headers  \n"
+	  "sloppiness =     file_macro   ,time_macros,  include_file_mtime,include_file_ctime,file_stat_matches,file_stat_matches_ctime,pch_defines ,  no_system_headers  \n"
 	  "stats = false\n"
 	  "temporary_dir = ${USER}_foo\n"
 	  "umask = 777\n"
@@ -169,8 +169,8 @@ TEST(conf_read_valid_config)
 	CHECK(!conf->run_second_cpp);
 	CHECK_INT_EQ(SLOPPY_INCLUDE_FILE_MTIME|SLOPPY_INCLUDE_FILE_CTIME|
 	             SLOPPY_FILE_MACRO|SLOPPY_TIME_MACROS|
-	             SLOPPY_FILE_STAT_MATCHES|SLOPPY_NO_SYSTEM_HEADERS|
-	             SLOPPY_PCH_DEFINES,
+	             SLOPPY_FILE_STAT_MATCHES|SLOPPY_FILE_STAT_MATCHES_CTIME|
+	             SLOPPY_NO_SYSTEM_HEADERS|SLOPPY_PCH_DEFINES,
 	             conf->sloppiness);
 	CHECK(!conf->stats);
 	CHECK_STR_EQ_FREE1(format("%s_foo", user), conf->temporary_dir);
@@ -414,8 +414,8 @@ TEST(conf_print_items)
 		.run_second_cpp = false,
 		SLOPPY_FILE_MACRO|SLOPPY_INCLUDE_FILE_MTIME|
 		SLOPPY_INCLUDE_FILE_CTIME|SLOPPY_TIME_MACROS|
-		SLOPPY_FILE_STAT_MATCHES|SLOPPY_PCH_DEFINES|
-		SLOPPY_NO_SYSTEM_HEADERS,
+		SLOPPY_FILE_STAT_MATCHES|SLOPPY_FILE_STAT_MATCHES_CTIME|
+		SLOPPY_PCH_DEFINES|SLOPPY_NO_SYSTEM_HEADERS,
 		false,
 		"td",
 		022,
@@ -465,7 +465,7 @@ TEST(conf_print_items)
 	CHECK_STR_EQ("run_second_cpp = false", received_conf_items[n++].descr);
 	CHECK_STR_EQ("sloppiness = file_macro, include_file_mtime,"
 	             " include_file_ctime, time_macros, pch_defines,"
-	             " file_stat_matches, no_system_headers",
+	             " file_stat_matches, file_stat_matches_ctime, no_system_headers",
 	             received_conf_items[n++].descr);
 	CHECK_STR_EQ("stats = false", received_conf_items[n++].descr);
 	CHECK_STR_EQ("temporary_dir = td", received_conf_items[n++].descr);