add readme

README.md

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+## Description
+texdepends is a small tool that scans given latex files for the following macros:
+- \input{}
+- \include{}
+- \lstinputlisting{}
+and lists all the files included using these macros in a file with either a given name
+or with the name of the processed file and a .d extension, using makefile dependency syntax.
+
+This means for a file that uses e.g. `\input{Intro.tex}` somewhere (the file is named `document.tex`}, 
+a call to `texdepends document.tex` will generate a file called `document.d` with the following content:
+```makefile
+document.tex: Intro.tex\ 
+```
+
+This file can be used to trigger a rebuild using make of the document if there were changes in files affecting it.
+
+## Command line options
+
+There are two possible switches:
+
+| Name | Description |
+| --:|:-- |
+| --target |  |
+| -t        | Can be used to set the string output before the colon char |
+| | |
+| --output: | |
+| -o:       | modifies the behaviour so all file dependencies of all input files will be written to the given file, instead of creating one file per input. |
+
+
+**Note: The --output switch should be used in combination with --target, because otherwise no target will be present in the output file!**
+
+## Building
+The Program is currently only written for Linux, i will see if a windows port is feasible (should be straight forward).
+
+### Linux
+Under Linux, a call to `make` should build produce a binary called `texdepends`.
+A simple test can be performed using `make test`
+
+## Notes
+
+- The program will follow all found *.tex links and parse them too, if possible. Files included in included files will therefore also show up as dependencies. It will only parse a file once
+- This is no latex parser, it has two major drawbacks:
+    - No Parsing of `\if`-directives, which means, that files included via `\if` will always show up
+    - No parsing of arguments to macros. The Only macro-supsitution happens inside `\include` or `\input` arguments. The only macro definitions supsituted are those made via `\def`. Therefore the following include will not show up in the output because it happend in a macro-argument.
+
+```
+\frame{
+    \include{Intro.tex}
+}
+```
+
+