Add template functionality

README.md

@@ -223,10 +223,34 @@ shown below:
 
 Homemaker will process the dependency tasks before processing the task itself.
 
-In addition to creating links, Homemaker is capable of executing commands on a per-task basis. Commands should be
-defined in an array called `cmds`, split into an item per each command line argument. All of the commands are executed
-with `dest` as the working directory (as mentioned previously, this defaults to your home directory). If any command
-returns a nonzero exit code, Homemaker will display an error message and prompt the user to determine if it should
+Sometimes, just linking a config file is not enough, because the content of the configuration file needs to be adapted
+to the target and we do not want to maintain several different versions of the same file. For such use cases, Homemaker
+supports templates. The configuration syntax for templates is the same as for links.
+
+```
+[tasks.template]
+    templates = [
+        [".gitconfig"]
+    ]
+```
+
+In the template file, the [go templating systax](https://godoc.org/text/template) is used for the customization of the 
+config file. With the `.Env` prefix, all environment variables are available. Template example:
+
+```
+[user]
+name = John Doe
+{{ if eq .Env.USER "john" }}
+    email = john@doe.me
+{{ else }}
+    email = john.doe@work.com
+{{ end }}
+```
+
+In addition to creating links and processing templates, Homemaker is capable of executing commands on a per-task basis.
+Commands should be defined in an array called `cmds`, split into an item per each command line argument. All of the commands
+are executed with `dest` as the working directory (as mentioned previously, this defaults to your home directory). If any
+command returns a nonzero exit code, Homemaker will display an error message and prompt the user to determine if it should
 *abort*, *retry*, or *cancel*. Additionally, if you must have explicit control of whether commands execute before or
 after the linking phase, you can use the `cmdspre` and `cmdspost` arrays which have similar behavior.
 

homemaker.go

@@ -36,6 +36,7 @@ const (
 	flagVerbose
 	flagNoCmds
 	flagNoLinks
+	flagNoTemplates
 	flagNoMacro
 	flagUnlink = flagNoCmds | (1 << iota)
 )
@@ -55,6 +56,7 @@ func main() {
 	verbose := flag.Bool("verbose", false, "verbose output")
 	nocmds := flag.Bool("nocmds", false, "don't execute commands")
 	nolinks := flag.Bool("nolinks", false, "don't create links")
+	notemplates := flag.Bool("notemplates", false, "don't process templates")
 	variant := flag.String("variant", "", "execution variant for tasks and macros")
 	unlink := flag.Bool("unlink", false, "remove existing links instead of creating them")
 
@@ -77,6 +79,9 @@ func main() {
 	if *nolinks {
 		flags |= flagNoLinks
 	}
+	if *notemplates {
+		flags |= flagNoTemplates
+	}
 	if *unlink {
 		flags |= flagUnlink
 	}

task.go

@@ -36,6 +36,7 @@ type task struct {
 	Envs      [][]string
 	Accepts   [][]string
 	Rejects   [][]string
+	Templates [][]string
 }
 
 func (t *task) deps(conf *config) []string {
@@ -85,6 +86,14 @@ func (t *task) process(conf *config) error {
 		}
 	}
 
+	if conf.flags&flagNoTemplates == 0 {
+		for _, currTmpl := range t.Templates {
+			if err := processTemplate(currTmpl, conf); err != nil {
+				return err
+			}
+		}
+	}
+
 	if conf.flags&flagNoCmds == 0 {
 		for _, currCmd := range t.CmdsPost {
 			if err := processCmd(currCmd, true, conf); err != nil {

template.go

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2015 Alex Yatskov <alex@foosoft.net>
+ * Author: Alex Yatskov <alex@foosoft.net>, Lucas Bremgartner <lucas@bremis.ch>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+	"text/template"
+)
+
+type context struct {
+}
+
+func (c *context) Env() map[string]string {
+	env := make(map[string]string)
+	for _, i := range os.Environ() {
+		sep := strings.Index(i, "=")
+		env[i[0:sep]] = i[sep+1:]
+	}
+	return env
+}
+
+func parseTemplate(params []string) (srcPath, dstPath string, mode os.FileMode, err error) {
+	length := len(params)
+	if length < 1 || length > 3 {
+		err = fmt.Errorf("invalid template statement")
+		return
+	}
+
+	if length > 2 {
+		var parsed uint64
+		parsed, err = strconv.ParseUint(params[2], 0, 64)
+		if err != nil {
+			return
+		}
+
+		mode = os.FileMode(parsed)
+	} else {
+		mode = 0755
+	}
+
+	dstPath = os.ExpandEnv(params[0])
+	srcPath = dstPath
+	if length > 1 {
+		srcPath = os.ExpandEnv(params[1])
+	}
+
+	return
+}
+
+func processTemplate(params []string, conf *config) (err error) {
+	srcPath, dstPath, mode, err := parseTemplate(params)
+	if err != nil {
+		return err
+	}
+
+	srcPathAbs := srcPath
+	if !path.IsAbs(srcPathAbs) {
+		srcPathAbs = path.Join(conf.srcDir, srcPath)
+	}
+
+	dstPathAbs := dstPath
+	if !path.IsAbs(dstPathAbs) {
+		dstPathAbs = path.Join(conf.dstDir, dstPath)
+	}
+
+	if _, err = os.Stat(srcPathAbs); os.IsNotExist(err) {
+		return fmt.Errorf("source path %s does not exist in filesystem", srcPathAbs)
+	}
+
+	if err = try(func() error { return createPath(dstPathAbs, conf.flags, mode) }); err != nil {
+		return err
+	}
+
+	if err = try(func() error { return cleanPath(dstPathAbs, conf.flags) }); err != nil {
+		return err
+	}
+
+	if conf.flags&flagVerbose != 0 {
+		log.Printf("process template %s to %s", srcPathAbs, dstPathAbs)
+	}
+
+	t, err := template.New(srcPath).ParseFiles(srcPathAbs)
+	if err != nil {
+		return err
+	}
+
+	f, err := os.Create(dstPathAbs)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		err = f.Close()
+	}()
+
+	return try(func() error {
+		return t.Execute(f, &context{})
+	})
+}