merge(3p/git): Merge git subtree at v2.29.2

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

third_party/git/compat/win32/path-utils.c

@@ -1,5 +1,29 @@
 #include "../../git-compat-util.h"
 
+int win32_has_dos_drive_prefix(const char *path)
+{
+	int i;
+
+	/*
+	 * Does it start with an ASCII letter (i.e. highest bit not set),
+	 * followed by a colon?
+	 */
+	if (!(0x80 & (unsigned char)*path))
+		return *path && path[1] == ':' ? 2 : 0;
+
+	/*
+	 * While drive letters must be letters of the English alphabet, it is
+	 * possible to assign virtually _any_ Unicode character via `subst` as
+	 * a drive letter to "virtual drives". Even `1`, or `ä`. Or fun stuff
+	 * like this:
+	 *
+	 *      subst ֍: %USERPROFILE%\Desktop
+	 */
+	for (i = 1; i < 4 && (0x80 & (unsigned char)path[i]); i++)
+		; /* skip first UTF-8 character */
+	return path[i] == ':' ? i + 1 : 0;
+}
+
 int win32_skip_dos_drive_prefix(char **path)
 {
 	int ret = has_dos_drive_prefix(*path);

third_party/git/compat/win32/path-utils.h

@@ -1,5 +1,9 @@
-#define has_dos_drive_prefix(path) \
-	(isalpha(*(path)) && (path)[1] == ':' ? 2 : 0)
+#ifndef WIN32_PATH_UTILS_H
+#define WIN32_PATH_UTILS_H
+
+int win32_has_dos_drive_prefix(const char *path);
+#define has_dos_drive_prefix win32_has_dos_drive_prefix
+
 int win32_skip_dos_drive_prefix(char **path);
 #define skip_dos_drive_prefix win32_skip_dos_drive_prefix
 static inline int win32_is_dir_sep(int c)
@@ -16,5 +20,18 @@ static inline char *win32_find_last_dir_sep(const char *path)
 	return ret;
 }
 #define find_last_dir_sep win32_find_last_dir_sep
+static inline int win32_has_dir_sep(const char *path)
+{
+	/*
+	 * See how long the non-separator part of the given path is, and
+	 * if and only if it covers the whole path (i.e. path[len] is NUL),
+	 * there is no separator in the path---otherwise there is a separator.
+	 */
+	size_t len = strcspn(path, "/\\");
+	return !!path[len];
+}
+#define has_dir_sep(path) win32_has_dir_sep(path)
 int win32_offset_1st_component(const char *path);
 #define offset_1st_component win32_offset_1st_component
+
+#endif

third_party/git/compat/win32/pthread.h

@@ -50,8 +50,8 @@ typedef struct {
 	DWORD tid;
 } pthread_t;
 
-extern int pthread_create(pthread_t *thread, const void *unused,
-			  void *(*start_routine)(void*), void *arg);
+int pthread_create(pthread_t *thread, const void *unused,
+		   void *(*start_routine)(void*), void *arg);
 
 /*
  * To avoid the need of copying a struct, we use small macro wrapper to pass
@@ -59,10 +59,10 @@ extern int pthread_create(pthread_t *thread, const void *unused,
  */
 #define pthread_join(a, b) win32_pthread_join(&(a), (b))
 
-extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
+int win32_pthread_join(pthread_t *thread, void **value_ptr);
 
 #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
-extern pthread_t pthread_self(void);
+pthread_t pthread_self(void);
 
 static inline void NORETURN pthread_exit(void *ret)
 {