29 files changed, 328 insertions, 60 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index ccaea39752..3263245b03 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -258,6 +258,14 @@ For C programs:
    ensure your patch is clear of all compiler warnings we care about,
    by e.g. "echo DEVELOPER=1 >>config.mak".
 
+ - When using DEVELOPER=1 mode, you may see warnings from the compiler
+   like "error: unused parameter 'foo' [-Werror=unused-parameter]",
+   which indicates that a function ignores its argument. If the unused
+   parameter can't be removed (e.g., because the function is used as a
+   callback and has to match a certain interface), you can annotate
+   the individual parameters with the UNUSED (or MAYBE_UNUSED)
+   keyword, like "int foo UNUSED".
+
  - We try to support a wide range of C compilers to compile Git with,
    including old ones.  As of Git v2.35.0 Git requires C99 (we check
    "__STDC_VERSION__"). You should not use features from a newer C
diff --git a/Documentation/RelNotes/2.47.0.txt b/Documentation/RelNotes/2.47.0.txt
index f614056467..7d4ac729f8 100644
--- a/Documentation/RelNotes/2.47.0.txt
+++ b/Documentation/RelNotes/2.47.0.txt
@@ -48,6 +48,9 @@ UI, Workflows & Features
 
  * Support for the RUNTIME_PREFIX feature has been added to z/OS port.
 
+ * "git send-email" learned "--mailmap" option to allow rewriting the
+   recipient addresses.
+
 
 Performance, Internal Implementation, Development Support etc.
 --------------------------------------------------------------
@@ -111,6 +114,9 @@ Performance, Internal Implementation, Development Support etc.
  * More trace2 events at key points on push and fetch code paths have
    been added.
 
+ * Make our codebase compilable with the -Werror=unused-parameter
+   option.
+
 
 Fixes since v2.46
 -----------------
diff --git a/Documentation/git-check-mailmap.txt b/Documentation/git-check-mailmap.txt
index 02f4418323..966c91c46a 100644
--- a/Documentation/git-check-mailmap.txt
+++ b/Documentation/git-check-mailmap.txt
@@ -15,10 +15,10 @@ SYNOPSIS
 DESCRIPTION
 -----------
 
-For each ``Name $$<user@host>$$'' or ``$$<user@host>$$'' from the command-line
-or standard input (when using `--stdin`), look up the person's canonical name
-and email address (see "Mapping Authors" below). If found, print them;
-otherwise print the input as-is.
+For each ``Name $$<user@host>$$'', ``$$<user@host>$$'', or ``$$user@host$$''
+from the command-line or standard input (when using `--stdin`), look up the
+person's canonical name and email address (see "Mapping Authors" below). If
+found, print them; otherwise print the input as-is.
 
 
 OPTIONS
@@ -27,6 +27,16 @@ OPTIONS
 	Read contacts, one per line, from the standard input after exhausting
 	contacts provided on the command-line.
 
+--mailmap-file=<file>::
+	In addition to any configured mailmap files, read the specified
+	mailmap file. Entries in this file take precedence over entries in
+	either the default mailmap file or any configured mailmap file.
+
+--mailmap-blob=<blob>::
+	Like `--mailmap-file`, but consider the value as a reference to a
+	blob in the repository. If both `--mailmap-file` and
+	`--mailmap-blob` are specified, entries in `--mailmap-file` will
+	take precedence.
 
 OUTPUT
 ------
diff --git a/builtin/check-mailmap.c b/builtin/check-mailmap.c
index b8a05b8e07..2334b57222 100644
--- a/builtin/check-mailmap.c
+++ b/builtin/check-mailmap.c
@@ -9,6 +9,7 @@
 #include "write-or-die.h"
 
 static int use_stdin;
+static const char *mailmap_file, *mailmap_blob;
 static const char * const check_mailmap_usage[] = {
 N_("git check-mailmap [<options>] <contact>..."),
 NULL
@@ -16,6 +17,8 @@ NULL
 
 static const struct option check_mailmap_options[] = {
 	OPT_BOOL(0, "stdin", &use_stdin, N_("also read contacts from stdin")),
+	OPT_FILENAME(0, "mailmap-file", &mailmap_file, N_("read additional mailmap entries from file")),
+	OPT_STRING(0, "mailmap-blob", &mailmap_blob, N_("blob"), N_("read additional mailmap entries from blob")),
 	OPT_END()
 };
 
@@ -25,13 +28,17 @@ static void check_mailmap(struct string_list *mailmap, const char *contact)
 	size_t namelen, maillen;
 	struct ident_split ident;
 
-	if (split_ident_line(&ident, contact, strlen(contact)))
-		die(_("unable to parse contact: %s"), contact);
-
-	name = ident.name_begin;
-	namelen = ident.name_end - ident.name_begin;
-	mail = ident.mail_begin;
-	maillen = ident.mail_end - ident.mail_begin;
+	if (!split_ident_line(&ident, contact, strlen(contact))) {
+		name = ident.name_begin;
+		namelen = ident.name_end - ident.name_begin;
+		mail = ident.mail_begin;
+		maillen = ident.mail_end - ident.mail_begin;
+	} else {
+		name = NULL;
+		namelen = 0;
+		mail = contact;
+		maillen = strlen(contact);
+	}
 
 	map_user(mailmap, &mail, &maillen, &name, &namelen);
 
@@ -52,6 +59,10 @@ int cmd_check_mailmap(int argc, const char **argv, const char *prefix)
 		die(_("no contacts specified"));
 
 	read_mailmap(&mailmap);
+	if (mailmap_blob)
+		read_mailmap_blob(&mailmap, mailmap_blob);
+	if (mailmap_file)
+		read_mailmap_file(&mailmap, mailmap_file, 0);
 
 	for (i = 0; i < argc; ++i)
 		check_mailmap(&mailmap, argv[i]);
diff --git a/builtin/gc.c b/builtin/gc.c
index 427faf1cfe..7dac971405 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -260,7 +260,7 @@ static int pack_refs_condition(UNUSED struct gc_config *cfg)
 	return 1;
 }
 
-static int maintenance_task_pack_refs(MAYBE_UNUSED struct maintenance_run_opts *opts,
+static int maintenance_task_pack_refs(struct maintenance_run_opts *opts,
 				      UNUSED struct gc_config *cfg)
 {
 	struct child_process cmd = CHILD_PROCESS_INIT;
@@ -967,7 +967,7 @@ static int dfs_on_ref(const char *refname UNUSED,
 	return result;
 }
 
-static int should_write_commit_graph(struct gc_config *cfg)
+static int should_write_commit_graph(struct gc_config *cfg UNUSED)
 {
 	int result;
 	struct cg_auto_data data;
@@ -1005,7 +1005,7 @@ static int run_write_commit_graph(struct maintenance_run_opts *opts)
 }
 
 static int maintenance_task_commit_graph(struct maintenance_run_opts *opts,
-					 struct gc_config *cfg)
+					 struct gc_config *cfg UNUSED)
 {
 	prepare_repo_settings(the_repository);
 	if (!the_repository->settings.core_commit_graph)
@@ -1040,7 +1040,7 @@ static int fetch_remote(struct remote *remote, void *cbdata)
 }
 
 static int maintenance_task_prefetch(struct maintenance_run_opts *opts,
-				     struct gc_config *cfg)
+				     struct gc_config *cfg UNUSED)
 {
 	if (for_each_remote(fetch_remote, opts)) {
 		error(_("failed to prefetch remotes"));
@@ -1051,7 +1051,7 @@ static int maintenance_task_prefetch(struct maintenance_run_opts *opts,
 }
 
 static int maintenance_task_gc(struct maintenance_run_opts *opts,
-			       struct gc_config *cfg)
+			       struct gc_config *cfg UNUSED)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
 
@@ -1100,7 +1100,7 @@ static int loose_object_count(const struct object_id *oid UNUSED,
 	return 0;
 }
 
-static int loose_object_auto_condition(struct gc_config *cfg)
+static int loose_object_auto_condition(struct gc_config *cfg UNUSED)
 {
 	int count = 0;
 
@@ -1192,12 +1192,12 @@ static int pack_loose(struct maintenance_run_opts *opts)
 }
 
 static int maintenance_task_loose_objects(struct maintenance_run_opts *opts,
-					  struct gc_config *cfg)
+					  struct gc_config *cfg UNUSED)
 {
 	return prune_packed(opts) || pack_loose(opts);
 }
 
-static int incremental_repack_auto_condition(struct gc_config *cfg)
+static int incremental_repack_auto_condition(struct gc_config *cfg UNUSED)
 {
 	struct packed_git *p;
 	int incremental_repack_auto_limit = 10;
@@ -1317,7 +1317,7 @@ static int multi_pack_index_repack(struct maintenance_run_opts *opts)
 }
 
 static int maintenance_task_incremental_repack(struct maintenance_run_opts *opts,
-					       struct gc_config *cfg)
+					       struct gc_config *cfg UNUSED)
 {
 	prepare_repo_settings(the_repository);
 	if (!the_repository->settings.core_multi_pack_index) {
diff --git a/compat/mingw.c b/compat/mingw.c
index 29d3f09768..eb13c02a76 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -243,7 +243,8 @@ static enum hide_dotfiles_type hide_dotfiles = HIDE_DOTFILES_DOTGITONLY;
 static char *unset_environment_variables;
 
 int mingw_core_config(const char *var, const char *value,
-		      const struct config_context *ctx, void *cb)
+		      const struct config_context *ctx UNUSED,
+		      void *cb UNUSED)
 {
 	if (!strcmp(var, "core.hidedotfiles")) {
 		if (value && !strcasecmp(value, "dotgitonly"))
@@ -453,7 +454,7 @@ static int set_hidden_flag(const wchar_t *path, int set)
 	return -1;
 }
 
-int mingw_mkdir(const char *path, int mode)
+int mingw_mkdir(const char *path, int mode UNUSED)
 {
 	int ret;
 	wchar_t wpath[MAX_PATH];
@@ -597,7 +598,7 @@ int mingw_open (const char *filename, int oflags, ...)
 	return fd;
 }
 
-static BOOL WINAPI ctrl_ignore(DWORD type)
+static BOOL WINAPI ctrl_ignore(DWORD type UNUSED)
 {
 	return TRUE;
 }
@@ -1085,7 +1086,7 @@ int mkstemp(char *template)
 	return git_mkstemp_mode(template, 0600);
 }
 
-int gettimeofday(struct timeval *tv, void *tz)
+int gettimeofday(struct timeval *tv, void *tz UNUSED)
 {
 	FILETIME ft;
 	long long hnsec;
@@ -2252,7 +2253,7 @@ char *mingw_query_user_email(void)
 	return get_extended_user_info(NameUserPrincipal);
 }
 
-struct passwd *getpwuid(int uid)
+struct passwd *getpwuid(int uid UNUSED)
 {
 	static unsigned initialized;
 	static char user_name[100];
@@ -2304,7 +2305,7 @@ static sig_handler_t timer_fn = SIG_DFL, sigint_fn = SIG_DFL;
  * length to call the signal handler.
  */
 
-static unsigned __stdcall ticktack(void *dummy)
+static unsigned __stdcall ticktack(void *dummy UNUSED)
 {
 	while (WaitForSingleObject(timer_event, timer_interval) == WAIT_TIMEOUT) {
 		mingw_raise(SIGALRM);
@@ -2352,7 +2353,7 @@ static inline int is_timeval_eq(const struct timeval *i1, const struct timeval *
 	return i1->tv_sec == i2->tv_sec && i1->tv_usec == i2->tv_usec;
 }
 
-int setitimer(int type, struct itimerval *in, struct itimerval *out)
+int setitimer(int type UNUSED, struct itimerval *in, struct itimerval *out)
 {
 	static const struct timeval zero;
 	static int atexit_done;
diff --git a/compat/mingw.h b/compat/mingw.h
index 27b61284f4..ebfb8ba423 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -122,17 +122,17 @@ struct utsname {
  * trivial stubs
  */
 
-static inline int readlink(const char *path, char *buf, size_t bufsiz)
+static inline int readlink(const char *path UNUSED, char *buf UNUSED, size_t bufsiz UNUSED)
 { errno = ENOSYS; return -1; }
-static inline int symlink(const char *oldpath, const char *newpath)
+static inline int symlink(const char *oldpath UNUSED, const char *newpath UNUSED)
 { errno = ENOSYS; return -1; }
-static inline int fchmod(int fildes, mode_t mode)
+static inline int fchmod(int fildes UNUSED, mode_t mode UNUSED)
 { errno = ENOSYS; return -1; }
 #ifndef __MINGW64_VERSION_MAJOR
 static inline pid_t fork(void)
 { errno = ENOSYS; return -1; }
 #endif
-static inline unsigned int alarm(unsigned int seconds)
+static inline unsigned int alarm(unsigned int seconds UNUSED)
 { return 0; }
 static inline int fsync(int fd)
 { return _commit(fd); }
@@ -140,9 +140,9 @@ static inline void sync(void)
 {}
 static inline uid_t getuid(void)
 { return 1; }
-static inline struct passwd *getpwnam(const char *name)
+static inline struct passwd *getpwnam(const char *name UNUSED)
 { return NULL; }
-static inline int fcntl(int fd, int cmd, ...)
+static inline int fcntl(int fd UNUSED, int cmd, ...)
 {
 	if (cmd == F_GETFD || cmd == F_SETFD)
 		return 0;
@@ -151,17 +151,17 @@ static inline int fcntl(int fd, int cmd, ...)
 }
 
 #define sigemptyset(x) (void)0
-static inline int sigaddset(sigset_t *set, int signum)
+static inline int sigaddset(sigset_t *set UNUSED, int signum UNUSED)
 { return 0; }
 #define SIG_BLOCK 0
 #define SIG_UNBLOCK 0
-static inline int sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
+static inline int sigprocmask(int how UNUSED, const sigset_t *set UNUSED, sigset_t *oldset UNUSED)
 { return 0; }
 static inline pid_t getppid(void)
 { return 1; }
 static inline pid_t getpgid(pid_t pid)
 { return pid == 0 ? getpid() : pid; }
-static inline pid_t tcgetpgrp(int fd)
+static inline pid_t tcgetpgrp(int fd UNUSED)
 { return getpid(); }
 
 /*
diff --git a/compat/nedmalloc/nedmalloc.c b/compat/nedmalloc/nedmalloc.c
index 2c0ace7075..145255da43 100644
--- a/compat/nedmalloc/nedmalloc.c
+++ b/compat/nedmalloc/nedmalloc.c
@@ -31,6 +31,8 @@ DEALINGS IN THE SOFTWARE.
 /*#pragma optimize("a", on)*/
 #endif
 
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+
 /*#define FULLSANITYCHECKS*/
 
 #include "nedmalloc.h"
diff --git a/compat/regex/regcomp.c b/compat/regex/regcomp.c
index 6c5d455e92..8d93a9b93f 100644
--- a/compat/regex/regcomp.c
+++ b/compat/regex/regcomp.c
@@ -17,6 +17,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+
 #if defined __TANDEM
  /* This is currently duplicated from git-compat-utils.h */
 # ifdef NO_INTPTR_T
diff --git a/compat/stub/procinfo.c b/compat/stub/procinfo.c
index 12c0a23c9e..3168cd5714 100644
--- a/compat/stub/procinfo.c
+++ b/compat/stub/procinfo.c
@@ -6,6 +6,6 @@
  * Stub. See sample implementations in compat/linux/procinfo.c and
  * compat/win32/trace2_win32_process_info.c.
  */
-void trace2_collect_process_info(enum trace2_process_info_reason reason)
+void trace2_collect_process_info(enum trace2_process_info_reason reason UNUSED)
 {
 }
diff --git a/compat/terminal.c b/compat/terminal.c
index 0afda730f2..d54efa1c5d 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c
@@ -594,7 +594,7 @@ void restore_term(void)
 {
 }
 
-char *git_terminal_prompt(const char *prompt, int echo)
+char *git_terminal_prompt(const char *prompt, int echo UNUSED)
 {
 	return getpass(prompt);
 }
diff --git a/compat/win32/headless.c b/compat/win32/headless.c
index 8b00dfe3bd..11392a0b9a 100644
--- a/compat/win32/headless.c
+++ b/compat/win32/headless.c
@@ -11,6 +11,8 @@
 #include <stdlib.h>
 #include <wchar.h>
 
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+
 /*
  * If `dir` contains the path to a Git exec directory, extend `PATH` to
  * include the corresponding `bin/` directory (which is where all those
diff --git a/compat/win32/pthread.c b/compat/win32/pthread.c
index 85f8f7920c..58980a529c 100644
--- a/compat/win32/pthread.c
+++ b/compat/win32/pthread.c
@@ -21,7 +21,7 @@ static unsigned __stdcall win32_start_routine(void *arg)
 	return 0;
 }
 
-int pthread_create(pthread_t *thread, const void *unused,
+int pthread_create(pthread_t *thread, const void *attr UNUSED,
 		   void *(*start_routine)(void *), void *arg)
 {
 	thread->arg = arg;
diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
index cc3221cb2c..e2b5c4f64c 100644
--- a/compat/win32/pthread.h
+++ b/compat/win32/pthread.h
@@ -18,7 +18,7 @@
  */
 #define pthread_mutex_t CRITICAL_SECTION
 
-static inline int return_0(int i) {
+static inline int return_0(int i UNUSED) {
 	return 0;
 }
 #define pthread_mutex_init(a,b) return_0((InitializeCriticalSection((a)), 0))
@@ -70,7 +70,7 @@ static inline void NORETURN pthread_exit(void *ret)
 }
 
 typedef DWORD pthread_key_t;
-static inline int pthread_key_create(pthread_key_t *keyp, void (*destructor)(void *value))
+static inline int pthread_key_create(pthread_key_t *keyp, void (*destructor)(void *value) UNUSED)
 {
 	return (*keyp = TlsAlloc()) == TLS_OUT_OF_INDEXES ? EAGAIN : 0;
 }
diff --git a/compat/win32/syslog.c b/compat/win32/syslog.c
index 0af18d8882..4e4794743a 100644
--- a/compat/win32/syslog.c
+++ b/compat/win32/syslog.c
@@ -2,7 +2,7 @@
 
 static HANDLE ms_eventlog;
 
-void openlog(const char *ident, int logopt, int facility)
+void openlog(const char *ident, int logopt UNUSED, int facility UNUSED)
 {
 	if (ms_eventlog)
 		return;
diff --git a/compat/win32mmap.c b/compat/win32mmap.c
index 519d51f2b6..a4ab4cb939 100644
--- a/compat/win32mmap.c
+++ b/compat/win32mmap.c
@@ -40,7 +40,7 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of
 	return MAP_FAILED;
 }
 
-int git_munmap(void *start, size_t length)
+int git_munmap(void *start, size_t length UNUSED)
 {
 	return !UnmapViewOfFile(start);
 }
diff --git a/compat/winansi.c b/compat/winansi.c
index 575813bde8..1b3f916b9f 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -340,7 +340,7 @@ enum {
 	TEXT = 0, ESCAPE = 033, BRACKET = '['
 };
 
-static DWORD WINAPI console_thread(LPVOID unused)
+static DWORD WINAPI console_thread(LPVOID data UNUSED)
 {
 	unsigned char buffer[BUFFER_SIZE];
 	DWORD bytes;
diff --git a/config.mak.dev b/config.mak.dev
index 5229c35484..50026d1e0e 100644
--- a/config.mak.dev
+++ b/config.mak.dev
@@ -54,7 +54,6 @@ ifeq ($(filter extra-all,$(DEVOPTS)),)
 DEVELOPER_CFLAGS += -Wno-empty-body
 DEVELOPER_CFLAGS += -Wno-missing-field-initializers
 DEVELOPER_CFLAGS += -Wno-sign-compare
-DEVELOPER_CFLAGS += -Wno-unused-parameter
 endif
 endif
 
diff --git a/git-compat-util.h b/git-compat-util.h
index 71b4d23f03..e4a306dd56 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -195,6 +195,19 @@ struct strbuf;
 #define _NETBSD_SOURCE 1
 #define _SGI_SOURCE 1
 
+/*
+ * UNUSED marks a function parameter that is always unused.  It also
+ * can be used to annotate a function, a variable, or a type that is
+ * always unused.
+ *
+ * A callback interface may dictate that a function accepts a
+ * parameter at that position, but the implementation of the function
+ * may not need to use the parameter.  In such a case, mark the parameter
+ * with UNUSED.
+ *
+ * When a parameter may be used or unused, depending on conditional
+ * compilation, consider using MAYBE_UNUSED instead.
+ */
 #if GIT_GNUC_PREREQ(4, 5)
 #define UNUSED __attribute__((unused)) \
 	__attribute__((deprecated ("parameter declared as UNUSED")))
@@ -649,6 +662,17 @@ static inline int git_has_dir_sep(const char *path)
 #define RESULT_MUST_BE_USED
 #endif
 
+/*
+ * MAYBE_UNUSED marks a function parameter that may be unused, but
+ * whose use is not an error.  It also can be used to annotate a
+ * function, a variable, or a type that may be unused.
+ *
+ * Depending on a configuration, all uses of such a thing may become
+ * #ifdef'ed away.  Marking it with UNUSED would give a warning in a
+ * compilation where it is indeed used, and not marking it at all
+ * would give a warning in a compilation where it is unused.  In such
+ * a case, MAYBE_UNUSED is the appropriate annotation to use.
+ */
 #define MAYBE_UNUSED __attribute__((__unused__))
 
 #include "compat/bswap.h"
diff --git a/git-send-email.perl b/git-send-email.perl
index cdcee1d0cf..c835d4c11a 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -47,6 +47,8 @@ git send-email --translate-aliases
     --compose-encoding      <str>  * Encoding to assume for introduction.
     --8bit-encoding         <str>  * Encoding to assume 8bit mails if undeclared
     --transfer-encoding     <str>  * Transfer encoding to use (quoted-printable, 8bit, base64)
+    --[no-]mailmap                 * Use mailmap file to map all email addresses to canonical
+                                     real names and email addresses.
 
   Sending:
     --envelope-sender       <str>  * Email envelope sender.
@@ -278,12 +280,14 @@ my (@suppress_cc);
 my ($auto_8bit_encoding);
 my ($compose_encoding);
 my ($sendmail_cmd);
+my ($mailmap_file, $mailmap_blob);
 # Variables with corresponding config settings & hardcoded defaults
 my ($debug_net_smtp) = 0;		# Net::SMTP, see send_message()
 my $thread = 1;
 my $chain_reply_to = 0;
 my $use_xmailer = 1;
 my $validate = 1;
+my $mailmap = 0;
 my $target_xfer_encoding = 'auto';
 my $forbid_sendmail_variables = 1;
 
@@ -300,6 +304,7 @@ my %config_bool_settings = (
     "annotate" => \$annotate,
     "xmailer" => \$use_xmailer,
     "forbidsendmailvariables" => \$forbid_sendmail_variables,
+    "mailmap" => \$mailmap,
 );
 
 my %config_settings = (
@@ -333,6 +338,8 @@ my %config_settings = (
 my %config_path_settings = (
     "aliasesfile" => \@alias_files,
     "smtpsslcertpath" => \$smtp_ssl_cert_path,
+    "mailmap.file" => \$mailmap_file,
+    "mailmap.blob" => \$mailmap_blob,
 );
 
 # Handle Uncouth Termination
@@ -533,6 +540,8 @@ my %options = (
 		    "thread!" => \$thread,
 		    "validate!" => \$validate,
 		    "transfer-encoding=s" => \$target_xfer_encoding,
+		    "mailmap!" => \$mailmap,
+		    "use-mailmap!" => \$mailmap,
 		    "format-patch!" => \$format_patch,
 		    "8bit-encoding=s" => \$auto_8bit_encoding,
 		    "compose-encoding=s" => \$compose_encoding,
@@ -1104,6 +1113,16 @@ if ($compose && $compose > 0) {
 our ($message_id, %mail, $subject, $in_reply_to, $references, $message,
 	$needs_confirm, $message_num, $ask_default);
 
+sub mailmap_address_list {
+	return @_ unless @_ and $mailmap;
+	my @options = ();
+	push(@options, "--mailmap-file=$mailmap_file") if $mailmap_file;
+	push(@options, "--mailmap-blob=$mailmap_blob") if $mailmap_blob;
+	my @addr_list = Git::command('check-mailmap', @options, @_);
+	s/^<(.*)>$/$1/ for @addr_list;
+	return @addr_list;
+}
+
 sub extract_valid_address {
 	my $address = shift;
 	my $local_part_regexp = qr/[^<>"\s@]+/;
@@ -1313,6 +1332,7 @@ sub process_address_list {
 	@addr_list = expand_aliases(@addr_list);
 	@addr_list = sanitize_address_list(@addr_list);
 	@addr_list = validate_address_list(@addr_list);
+	@addr_list = mailmap_address_list(@addr_list);
 	return @addr_list;
 }
 
diff --git a/grep.c b/grep.c
index 2f8b9553df..e5761426e4 100644
--- a/grep.c
+++ b/grep.c
@@ -245,7 +245,7 @@ static int is_fixed(const char *s, size_t len)
 #ifdef USE_LIBPCRE2
 #define GREP_PCRE2_DEBUG_MALLOC 0
 
-static void *pcre2_malloc(PCRE2_SIZE size, MAYBE_UNUSED void *memory_data)
+static void *pcre2_malloc(PCRE2_SIZE size, void *memory_data UNUSED)
 {
 	void *pointer = malloc(size);
 #if GREP_PCRE2_DEBUG_MALLOC
@@ -255,7 +255,7 @@ static void *pcre2_malloc(PCRE2_SIZE size, MAYBE_UNUSED void *memory_data)
 	return pointer;
 }
 
-static void pcre2_free(void *pointer, MAYBE_UNUSED void *memory_data)
+static void pcre2_free(void *pointer, void *memory_data UNUSED)
 {
 #if GREP_PCRE2_DEBUG_MALLOC
 	static int count = 1;
diff --git a/mailmap.c b/mailmap.c
index 2acf97f307..9f9fa3199a 100644
--- a/mailmap.c
+++ b/mailmap.c
@@ -142,11 +142,8 @@ static void read_mailmap_line(struct string_list *map, char *buffer)
 		add_mapping(map, name1, email1, name2, email2);
 }
 
-/* Flags for read_mailmap_file() */
-#define MAILMAP_NOFOLLOW (1<<0)
-
-static int read_mailmap_file(struct string_list *map, const char *filename,
-			     unsigned flags)
+int read_mailmap_file(struct string_list *map, const char *filename,
+		      unsigned flags)
 {
 	char buffer[1024];
 	FILE *f;
@@ -186,7 +183,7 @@ static void read_mailmap_string(struct string_list *map, char *buf)
 	}
 }
 
-static int read_mailmap_blob(struct string_list *map, const char *name)
+int read_mailmap_blob(struct string_list *map, const char *name)
 {
 	struct object_id oid;
 	char *buf;
diff --git a/mailmap.h b/mailmap.h
index cbda9bc5e0..908365e1bf 100644
--- a/mailmap.h
+++ b/mailmap.h
@@ -6,6 +6,13 @@ struct string_list;
 extern char *git_mailmap_file;
 extern char *git_mailmap_blob;
 
+/* Flags for read_mailmap_file() */
+#define MAILMAP_NOFOLLOW (1<<0)
+
+int read_mailmap_file(struct string_list *map, const char *filename,
+		      unsigned flags);
+int read_mailmap_blob(struct string_list *map, const char *name);
+
 int read_mailmap(struct string_list *map);
 void clear_mailmap(struct string_list *map);
 
diff --git a/mergetools/vscode b/mergetools/vscode
new file mode 100644
index 0000000000..3b39b458d6
--- /dev/null
+++ b/mergetools/vscode
@@ -0,0 +1,19 @@
+diff_cmd () {
+	"$merge_tool_path" --wait --diff "$LOCAL" "$REMOTE"
+}
+
+diff_cmd_help () {
+	echo "Use Visual Studio Code (requires a graphical session)"
+}
+
+merge_cmd () {
+	"$merge_tool_path" --wait --merge "$REMOTE" "$LOCAL" "$BASE" "$MERGED"
+}
+
+merge_cmd_help () {
+	echo "Use Visual Studio Code (requires a graphical session)"
+}
+
+translate_merge_tool_path () {
+	echo code
+}
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 1cff65f6ae..4c5573b19c 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1946,10 +1946,13 @@ static int commit_ref_update(struct files_ref_store *refs,
 	return 0;
 }
 
+#ifdef NO_SYMLINK_HEAD
+#define create_ref_symlink(a, b) (-1)
+#else
 static int create_ref_symlink(struct ref_lock *lock, const char *target)
 {
 	int ret = -1;
-#ifndef NO_SYMLINK_HEAD
+
 	char *ref_path = get_locked_file_path(&lock->lk);
 	unlink(ref_path);
 	ret = symlink(target, ref_path);
@@ -1957,9 +1960,9 @@ static int create_ref_symlink(struct ref_lock *lock, const char *target)
 
 	if (ret)
 		fprintf(stderr, "no symlink - falling back to symbolic ref\n");
-#endif
 	return ret;
 }
+#endif
 
 static int create_symref_lock(struct ref_lock *lock, const char *target,
 			      struct strbuf *err)
diff --git a/revision.c b/revision.c
index ac94f8d429..2d7ad2bddf 100644
--- a/revision.c
+++ b/revision.c
@@ -4407,6 +4407,7 @@ static struct commit *get_revision_internal(struct rev_info *revs)
 				c = get_revision_1(revs);
 				if (!c)
 					break;
+				free_commit_buffer(revs->repo->parsed_objects, c);
 			}
 		}
 
diff --git a/t/t4203-mailmap.sh b/t/t4203-mailmap.sh
index 79e5f42760..2265ff8872 100755
--- a/t/t4203-mailmap.sh
+++ b/t/t4203-mailmap.sh
@@ -72,12 +72,46 @@ test_expect_success 'check-mailmap --stdin arguments: mapping' '
 	test_cmp expect actual
 '
 
-test_expect_success 'check-mailmap bogus contact' '
-	test_must_fail git check-mailmap bogus
+test_expect_success 'check-mailmap simple address: mapping' '
+	test_when_finished "rm .mailmap" &&
+	cat >.mailmap <<-EOF &&
+	New Name <$GIT_AUTHOR_EMAIL>
+	EOF
+	cat .mailmap >expect &&
+	git check-mailmap "$GIT_AUTHOR_EMAIL" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'check-mailmap --stdin simple address: mapping' '
+	test_when_finished "rm .mailmap" &&
+	cat >.mailmap <<-EOF &&
+	New Name <$GIT_AUTHOR_EMAIL>
+	EOF
+	cat >stdin <<-EOF &&
+	$GIT_AUTHOR_EMAIL
+	EOF
+	cat .mailmap >expect &&
+	git check-mailmap --stdin <stdin >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'check-mailmap simple address: no mapping' '
+	cat >expect <<-EOF &&
+	<bugs@company.xx>
+	EOF
+	git check-mailmap "bugs@company.xx" >actual &&
+	test_cmp expect actual
 '
 
-test_expect_success 'check-mailmap bogus contact --stdin' '
-	test_must_fail git check-mailmap --stdin bogus </dev/null
+test_expect_success 'check-mailmap --stdin simple address: no mapping' '
+	cat >expect <<-EOF &&
+	<bugs@company.xx>
+	EOF
+	cat >stdin <<-EOF &&
+	bugs@company.xx
+	EOF
+	git check-mailmap --stdin <stdin >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'No mailmap' '
diff --git a/t/t9001-send-email.sh b/t/t9001-send-email.sh
index c5e862694e..df5336bb7e 100755
--- a/t/t9001-send-email.sh
+++ b/t/t9001-send-email.sh
@@ -2485,6 +2485,128 @@ test_expect_success $PREREQ 'leading and trailing whitespaces are removed' '
 	test_cmp expected-list actual-list
 '
 
+test_expect_success $PREREQ 'mailmap support with --to' '
+	clean_fake_sendmail &&
+	test_config mailmap.file "mailmap.test" &&
+	cat >mailmap.test <<-EOF &&
+	Some Body <someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--to=someone@example.org \
+		--mailmap \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
+test_expect_success $PREREQ 'sendemail.mailmap configuration' '
+	clean_fake_sendmail &&
+	test_config mailmap.file "mailmap.test" &&
+	test_config sendemail.mailmap "true" &&
+	cat >mailmap.test <<-EOF &&
+	Some Body <someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--to=someone@example.org \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
+test_expect_success $PREREQ 'sendemail.mailmap.file configuration' '
+	clean_fake_sendmail &&
+	test_config sendemail.mailmap.file "mailmap.test" &&
+	test_config sendemail.mailmap "true" &&
+	cat >mailmap.test <<-EOF &&
+	Some Body <someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--to=someone@example.org \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
+test_expect_success $PREREQ 'sendemail.mailmap identity overrides configuration' '
+	clean_fake_sendmail &&
+	test_config sendemail.cloud.mailmap.file "mailmap.test" &&
+	test_config sendemail.mailmap "false" &&
+	test_config sendemail.cloud.mailmap "true" &&
+	cat >mailmap.test <<-EOF &&
+	Some Body <someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--identity=cloud \
+		--to=someone@example.org \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
+test_expect_success $PREREQ '--no-mailmap overrides configuration' '
+	clean_fake_sendmail &&
+	test_config sendemail.cloud.mailmap.file "mailmap.test" &&
+	test_config sendemail.mailmap "false" &&
+	test_config sendemail.cloud.mailmap "true" &&
+	cat >mailmap.test <<-EOF &&
+	Some Body <someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--identity=cloud \
+		--to=someone@example.org \
+		--no-mailmap \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.org!$" commandline1
+'
+
+test_expect_success $PREREQ 'mailmap support in To header' '
+	clean_fake_sendmail &&
+	test_config mailmap.file "mailmap.test" &&
+	cat >mailmap.test <<-EOF &&
+	<someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 --to=someone@example.org >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--mailmap \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
+test_expect_success $PREREQ 'mailmap support in Cc header' '
+	clean_fake_sendmail &&
+	test_config mailmap.file "mailmap.test" &&
+	cat >mailmap.test <<-EOF &&
+	<someone@example.com> <someone@example.org>
+	EOF
+	git format-patch --stdout -1 --cc=someone@example.org >a.patch &&
+	git send-email \
+		--from="Example <nobody@example.com>" \
+		--smtp-server="$(pwd)/fake.sendmail" \
+		--mailmap \
+		a.patch \
+		2>errors >out &&
+	grep "^!someone@example\.com!$" commandline1
+'
+
 test_expect_success $PREREQ 'test using command name with --sendmail-cmd' '
 	clean_fake_sendmail &&
 	PATH="$PWD:$PATH" \
diff --git a/t/unit-tests/t-reftable-readwrite.c b/t/unit-tests/t-reftable-readwrite.c
index b4d7e7e76b..82bfaf3287 100644
--- a/t/unit-tests/t-reftable-readwrite.c
+++ b/t/unit-tests/t-reftable-readwrite.c
@@ -26,7 +26,7 @@ static ssize_t strbuf_add_void(void *b, const void *data, size_t sz)
 	return sz;
 }
 
-static int noop_flush(void *arg)
+static int noop_flush(void *arg UNUSED)
 {
 	return 0;
 }