[PATCH] git-am: fix detection of absolute paths for windows

[Pat Thoyts <patthoyts@users.sourceforge.net>]

Add an is_absolute_path function to abstract out platform differences
in checking for an absolute or relative path.
Specifically fixes t4150-am on Windows.

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
---

In response to the following comment...

>Johannes Sixt <j6t@kdbg.org> writes:
>>>       git-am: fix absolute path logic on Windows 
>>
>>This mistakes a file that has a colon in the second position as absolute, even 
>>on non-Windows. IIUC, this patch is not intended for upstream git.
>>

This patch is an alternative solution that only tries the Windows paths
on msysGit. This is_absolute_path might find use elsewhere in the future
so I elected to place it in the sh-setup script. Also added support for
identifying a UNC path as absolute.


 git-am.sh       |   12 ++++++------
 git-sh-setup.sh |   15 +++++++++++++++
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/git-am.sh b/git-am.sh
index e7f008c..9317b38 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -444,12 +444,12 @@ else
 				set x
 				first=
 			}
-			case "$arg" in
-			/*)
-				set "$@" "$arg" ;;
-			*)
-				set "$@" "$prefix$arg" ;;
-			esac
+			if is_absolute_path "$arg"
+			then
+				set "$@" "$arg"
+			else
+				set "$@" "$prefix$arg"
+			fi
 		done
 		shift
 	fi
diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 6131670..b9eb0bf 100644
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -209,5 +209,20 @@ case $(uname -s) in
 	find () {
 		/usr/bin/find "$@"
 	}
+	is_absolute_path () {
+		case "$1" in
+		/* | ?:* | \\\\*)
+			return 0 ;;
+		esac
+		return 1
+	}
 	;;
+*)
+	is_absolute_path () {
+		case "$1" in
+		/*)
+			return 0 ;;
+		esac
+		return 1
+	}
 esac
-- 
1.7.3