revert(3p/git): Revert merge of git upstream at v2.26.2 r/852

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232de5bfa959ad6ebbb4c8192ac513352, reversing
changes made to f2b211131f2347342dde63975b09cf603149f1a3.

1 files changed, 28 insertions, 3 deletions

diff --git a/third_party/git/compat/poll/poll.c b/third_party/git/compat/poll/poll.c
index afa6d245846a..0e95dd493c94 100644
--- a/third_party/git/compat/poll/poll.c
+++ b/third_party/git/compat/poll/poll.c
@@ -139,10 +139,22 @@ win32_compute_revents (HANDLE h, int *p_sought)
   INPUT_RECORD *irbuffer;
   DWORD avail, nbuffer;
   BOOL bRet;
+  IO_STATUS_BLOCK iosb;
+  FILE_PIPE_LOCAL_INFORMATION fpli;
+  static PNtQueryInformationFile NtQueryInformationFile;
+  static BOOL once_only;
 
   switch (GetFileType (h))
     {
     case FILE_TYPE_PIPE:
+      if (!once_only)
+	{
+	  NtQueryInformationFile = (PNtQueryInformationFile)(void (*)(void))
+	    GetProcAddress (GetModuleHandleW (L"ntdll.dll"),
+			    "NtQueryInformationFile");
+	  once_only = TRUE;
+	}
+
       happened = 0;
       if (PeekNamedPipe (h, NULL, 0, NULL, &avail, NULL) != 0)
 	{
@@ -154,9 +166,22 @@ win32_compute_revents (HANDLE h, int *p_sought)
 
       else
 	{
-	  /* It was the write-end of the pipe. Unfortunately there is no
-	     reliable way of knowing if it can be written without blocking.
-	     Just say that it's all good. */
+	  /* It was the write-end of the pipe.  Check if it is writable.
+	     If NtQueryInformationFile fails, optimistically assume the pipe is
+	     writable.  This could happen on Win9x, where NtQueryInformationFile
+	     is not available, or if we inherit a pipe that doesn't permit
+	     FILE_READ_ATTRIBUTES access on the write end (I think this should
+	     not happen since WinXP SP2; WINE seems fine too).  Otherwise,
+	     ensure that enough space is available for atomic writes.  */
+	  memset (&iosb, 0, sizeof (iosb));
+	  memset (&fpli, 0, sizeof (fpli));
+
+	  if (!NtQueryInformationFile
+	      || NtQueryInformationFile (h, &iosb, &fpli, sizeof (fpli),
+					 FilePipeLocalInformation)
+	      || fpli.WriteQuotaAvailable >= PIPE_BUF
+	      || (fpli.OutboundQuota < PIPE_BUF &&
+		  fpli.WriteQuotaAvailable == fpli.OutboundQuota))
 	    happened |= *p_sought & (POLLOUT | POLLWRNORM | POLLWRBAND);
 	}
       return happened;