'cmd/git.exe' not support launcher from symlink with other directory

[fcharlie]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

$ git --version --build-options

git version 2.17.0.windows.1
cpu: x86_64
built from commit: e7621d891d081acff6acd1f0ba6ae0adce06dd09
sizeof-long: 4

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [版本 10.0.17134.1]

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
> type "C:\Program Files (x86)\Git\etc\install-options.txt"
> type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

Editor Option: VIM
Path Option: BashOnly
SSH Option: OpenSSH
CURL Option: WinSSL
CRLF Option: CRLFCommitAsIs
Bash Terminal Option: MinTTY
Performance Tweaks FSCache: Enabled
Use Credential Manager: Enabled
Enable Symlinks: Enabled

cd %TEMP%
mklink git.exe "C:\Program Files\Git\cmd\git.exe"
git --help

output:

error launching git:

I think this launcher doesn't consider the symbolic link that may be returned by GetModuleFileName.

[dscho]

Oh, whoops! I missed this ticket.

Is this no longer an issue, @fcharlie?

[fcharlie]

@dscho This issue has not been resolved. But I have other solutions.

We can create a launcher startup git process(wait git).
https://github.com/fstudio/clangbuilder/blob/master/sources/template/link.template.console.cc

Readlink impl Support AppExecLink

#ifndef IO_REPARSE_TAG_APPEXECLINK
#define IO_REPARSE_TAG_APPEXECLINK (0x8000001BL)
#endif

// https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/content/ntifs/ns-ntifs-_reparse_data_buffer

typedef struct _REPARSE_DATA_BUFFER {
  ULONG ReparseTag;         // Reparse tag type
  USHORT ReparseDataLength; // Length of the reparse data
  USHORT Reserved;          // Used internally by NTFS to store remaining length

  union {
    // Structure for IO_REPARSE_TAG_SYMLINK
    // Handled by nt!IoCompleteRequest
    struct {
      USHORT SubstituteNameOffset;
      USHORT SubstituteNameLength;
      USHORT PrintNameOffset;
      USHORT PrintNameLength;
      ULONG Flags;
      WCHAR PathBuffer[1];
    } SymbolicLinkReparseBuffer;

    // Structure for IO_REPARSE_TAG_MOUNT_POINT
    // Handled by nt!IoCompleteRequest
    struct {
      USHORT SubstituteNameOffset;
      USHORT SubstituteNameLength;
      USHORT PrintNameOffset;
      USHORT PrintNameLength;
      WCHAR PathBuffer[1];
    } MountPointReparseBuffer;

    // Structure for IO_REPARSE_TAG_WIM
    // Handled by wimmount!FPOpenReparseTarget->wimserv.dll
    // (wimsrv!ImageExtract)
    struct {
      GUID ImageGuid;           // GUID of the mounted VIM image
      BYTE ImagePathHash[0x14]; // Hash of the path to the file within the image
    } WimImageReparseBuffer;

    // Structure for IO_REPARSE_TAG_WOF
    // Handled by FSCTL_GET_EXTERNAL_BACKING, FSCTL_SET_EXTERNAL_BACKING in NTFS
    // (Windows 10+)
    struct {
      //-- WOF_EXTERNAL_INFO --------------------
      ULONG Wof_Version;  // Should be 1 (WOF_CURRENT_VERSION)
      ULONG Wof_Provider; // Should be 2 (WOF_PROVIDER_FILE)

      //-- FILE_PROVIDER_EXTERNAL_INFO_V1 --------------------
      ULONG FileInfo_Version; // Should be 1 (FILE_PROVIDER_CURRENT_VERSION)
      ULONG
      FileInfo_Algorithm; // Usually 0 (FILE_PROVIDER_COMPRESSION_XPRESS4K)
    } WofReparseBuffer;

    // Structure for IO_REPARSE_TAG_APPEXECLINK
    struct {
      ULONG StringCount;   // Number of the strings in the StringList, separated
                           // by '\0'
      WCHAR StringList[1]; // Multistring (strings separated by '\0', terminated
                           // by '\0\0')
    } AppExecLinkReparseBuffer;

    // Dummy structure
    struct {
      UCHAR DataBuffer[1];
    } GenericReparseBuffer;
  } DUMMYUNIONNAME;
} REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;
struct ReparseBuffer {
  ReparseBuffer() {
    data = reinterpret_cast<REPARSE_DATA_BUFFER *>(
        malloc(MAXIMUM_REPARSE_DATA_BUFFER_SIZE));
  }
  ~ReparseBuffer() {
    if (data != nullptr) {
      free(data);
    }
  }
  REPARSE_DATA_BUFFER *data{nullptr};
};
bool Readlink(const std::wstring &symfile, std::wstring &realfile) {
  auto hFile = CreateFileW(
      symfile.c_str(), 0,
      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr,
      OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
      nullptr);
  if (hFile == INVALID_HANDLE_VALUE) {
    ErrorMessage err(GetLastError());
    fwprintf(stderr, L"CreateFileW: %s\n", err.message());
    return false;
  }
  ReparseBuffer rbuf;
  DWORD dwBytes = 0;
  if (DeviceIoControl(hFile, FSCTL_GET_REPARSE_POINT, nullptr, 0, rbuf.data,
                      MAXIMUM_REPARSE_DATA_BUFFER_SIZE, &dwBytes,
                      nullptr) != TRUE) {
    ErrorMessage err(GetLastError());
    fwprintf(stderr, L"DeviceIoControl: %s\n", err.message());
    CloseHandle(hFile);
    return false;
  }
  CloseHandle(hFile);
  switch (rbuf.data->ReparseTag) {
  case IO_REPARSE_TAG_SYMLINK: {
    auto wstr = rbuf.data->SymbolicLinkReparseBuffer.PathBuffer +
                (rbuf.data->SymbolicLinkReparseBuffer.SubstituteNameOffset /
                 sizeof(WCHAR));
    auto wlen = rbuf.data->SymbolicLinkReparseBuffer.SubstituteNameLength /
                sizeof(WCHAR);
    if (wlen >= 4 && wstr[0] == L'\\' && wstr[1] == L'?' && wstr[2] == L'?' &&
        wstr[3] == L'\\') {
      /* Starts with \??\ */
      if (wlen >= 6 &&
          ((wstr[4] >= L'A' && wstr[4] <= L'Z') ||
           (wstr[4] >= L'a' && wstr[4] <= L'z')) &&
          wstr[5] == L':' && (wlen == 6 || wstr[6] == L'\\')) {
        /* \??\<drive>:\ */
        wstr += 4;
        wlen -= 4;

      } else if (wlen >= 8 && (wstr[4] == L'U' || wstr[4] == L'u') &&
                 (wstr[5] == L'N' || wstr[5] == L'n') &&
                 (wstr[6] == L'C' || wstr[6] == L'c') && wstr[7] == L'\\') {
        /* \??\UNC\<server>\<share>\ - make sure the final path looks like */
        /* \\<server>\<share>\ */
        wstr += 6;
        wstr[0] = L'\\';
        wlen -= 6;
      }
    }
    realfile.assign(wstr, wlen);
  } break;
  case IO_REPARSE_TAG_MOUNT_POINT: {
    auto wstr = rbuf.data->MountPointReparseBuffer.PathBuffer +
                (rbuf.data->MountPointReparseBuffer.SubstituteNameOffset /
                 sizeof(WCHAR));
    auto wlen =
        rbuf.data->MountPointReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
    /* Only treat junctions that look like \??\<drive>:\ as symlink. */
    /* Junctions can also be used as mount points, like \??\Volume{<guid>}, */
    /* but that's confusing for programs since they wouldn't be able to */
    /* actually understand such a path when returned by uv_readlink(). */
    /* UNC paths are never valid for junctions so we don't care about them. */
    if (!(wlen >= 6 && wstr[0] == L'\\' && wstr[1] == L'?' && wstr[2] == L'?' &&
          wstr[3] == L'\\' &&
          ((wstr[4] >= L'A' && wstr[4] <= L'Z') ||
           (wstr[4] >= L'a' && wstr[4] <= L'z')) &&
          wstr[5] == L':' && (wlen == 6 || wstr[6] == L'\\'))) {
      SetLastError(ERROR_SYMLINK_NOT_SUPPORTED);
      return false;
    }

    /* Remove leading \??\ */
    wstr += 4;
    wlen -= 4;
    realfile.assign(wstr, wlen);
  } break;
  case IO_REPARSE_TAG_APPEXECLINK: {
    if (rbuf.data->AppExecLinkReparseBuffer.StringCount != 0) {
      LPWSTR szString = (LPWSTR)rbuf.data->AppExecLinkReparseBuffer.StringList;
      for (ULONG i = 0; i < rbuf.data->AppExecLinkReparseBuffer.StringCount;
           i++) {
        if (i == 2) {
          realfile = szString;
        }
        szString += wcslen(szString) + 1;
      }
    }
  } break;
  default:
    return false;
  }
  return true;
}

[fcharlie]

@dscho Look like mingw-w64-git/git-wrapper.c doesn't resolve symbolic links.

[fcharlie]

@dscho I added a PR to fix this issues git-for-windows/MINGW-packages#30