I have been using Git from last few days, and faced following errors while committing:

1) Trailing whitespace
2) Indent SP followed by a TAB
3) Unresolved merge conflict

The first error “Trailing whitespace” is because of carriage-return/line-feed(windows style line feed/end). To resolve this problem comment following lines(58-60) in .git/hooks/pre-commit file:

  if (/\s$/) {
    bad_line("trailing whitespace", $_);
 }

The second one “Indent SP followed by a TAB” is because of leading spaces/tabs. To resolve this problem comment following lines(61-63) in .git/hooks/pre-commit file:

  if (/^\s*   /) {
    bad_line("indent SP followed by a TAB", $_);
  }

The third one “Unresolved merge conflict” is because of seven or more successive occurrence of = or < or > characters. Major chances of having seven = character in README or doc files. To resolve this problem replace following line(64) in .git/hooks/pre-commit file:

  if (/^(?:[<>=]){7}/) {

by

  if (/^(?:[<>=]){7}$/) {

These tricks worked for me, I hope it could help you.