Add Windows support to make

Author: Mikulas

INSTALL

@@ -70,3 +70,17 @@ and does not currently create key files with restrictive permissions,
 making it unsuitable for use on a multi-user system.  Windows support
 will mature in a future version of git-crypt.  Bug reports and patches
 are most welcome!
+
+Instructions:
+
+- Download and install 32bit OpenSSL development binaries (the full ~16BM
+package) from https://slproweb.com/products/Win32OpenSSL.html.
+The 64bit packages do not include linked MinGW libraries! Let it
+install to the default location (C:\OpenSSL-Win32) or update
+WIN_OPENSSL32_DIR in Makefile.
+
+- Install MinGW from http://www.mingw.org/wiki/Getting_Started and
+install the full mingw-developer-toolkit.
+
+- Checkout git-crypt and invoke make in command line to build
+the Windows executable.

INSTALL.md

@@ -69,3 +69,17 @@ and does not currently create key files with restrictive permissions,
 making it unsuitable for use on a multi-user system.  Windows support
 will mature in a future version of git-crypt.  Bug reports and patches
 are most welcome!
+
+Instructions:
+
+- Download and install 32bit OpenSSL development binaries (the full ~16BM
+package) from https://slproweb.com/products/Win32OpenSSL.html.
+The 64bit packages do not include linked MinGW libraries! Let it
+install to the default location (`C:\OpenSSL-Win32`) or update
+`WIN_OPENSSL32_DIR` in Makefile.
+
+- Install MinGW from http://www.mingw.org/wiki/Getting_Started and
+install the full `mingw-developer-toolkit`.
+
+- Checkout `git-crypt` and invoke `make` in command line to build
+the Windows executable.

Makefile

@@ -24,14 +24,21 @@ OBJFILES = \
     fhstream.o
 
 OBJFILES += crypto-openssl.o
-LDFLAGS += -lcrypto
 
 XSLTPROC ?= xsltproc
 DOCBOOK_FLAGS += --param man.output.in.separate.dir 1 \
 		 --stringparam man.output.base.dir man/ \
 		 --param man.output.subdirs.enabled 1 \
 		 --param man.authors.section.enabled 1
 
+ifeq ($(OS),Windows_NT)
+	WIN_OPENSSL32_DIR ?= C:\OpenSSL-Win32
+	CXXFLAGS += -I$(WIN_OPENSSL32_DIR)\include
+	LDFLAGS += $(WIN_OPENSSL32_DIR)\lib\MinGW\libeay32.a
+else
+	LDFLAGS += -lcrypto
+endif
+
 all: build
 
 #