Document & test simple post-process solution

Fixes #5 (alternative fix)

README.md

@@ -58,9 +58,18 @@ If you're not seeing what you expect, then start with this:
 
 ## Custom version string
 
-To define a custom version string you can use `dynverGitDescribeOutput`, `dynverCurrentDate` and `sbtdynver.DynVer` object to redefine `version in ThisBuild` (and optionally also `dynver in ThisBuild`).
+Sometimes you want to customise the version string. It might be for personal preference, or for compatibility with another tool or spec.
 
-For example if you want a custom version string that doesn't use `+`'s (because Docker rejects them - [#5](https://github.com/dwijnand/sbt-dynver/issues/5)) you can customise like so:
+As an example, Docker rejects tags which include `+`'s ([#5](https://github.com/dwijnand/sbt-dynver/issues/5).
+
+A simply way to solve this is to simply post-process the value of `version in ThisBuild` (and optionally `dynver in ThisBuild`), for example by replacing '+' with '-':
+
+```scala
+version in ThisBuild ~= (_.replace('+', '-'))
+ dynver in ThisBuild ~= (_.replace('+', '-'))
+```
+
+If instead you want to completely customise the string format you can use `dynverGitDescribeOutput`, `dynverCurrentDate` and `sbtdynver.DynVer`, like so:
 
 ```scala
 def versionFmt(out: sbtdynver.GitDescribeOutput): String =
@@ -77,7 +86,7 @@ inThisBuild(List(
 ))
 ```
 
-Essentially this defines how to transform `git describe`'s output into a string, what the fallback version string is, and then wires everything back together.
+Essentially this defines how to transform the structured output of `git describe`'s into a string, defines the fallback version string, and then wires everything back together.
 
 ## Dependencies
 

src/sbt-test/dynver/custom-version-string-0/build.sbt

@@ -0,0 +1,32 @@
+version in ThisBuild ~= (_.replace('+', '-'))
+ dynver in ThisBuild ~= (_.replace('+', '-'))
+
+def tstamp = Def.setting(sbtdynver.DynVer timestamp dynverCurrentDate.value)
+def headSha = Def.task("git rev-parse --short=8 HEAD".!!(streams.value.log).trim)
+
+def check(a: String, e: String) = assert(a == e, s"Version mismatch: Expected $e, Incoming $a")
+
+TaskKey[Unit]("checkNotAGitRepo")         := check(version.value, s"HEAD-${tstamp.value}")
+TaskKey[Unit]("checkNoCommits")           := check(version.value, s"HEAD-${tstamp.value}")
+TaskKey[Unit]("checkOnCommit")            := check(version.value, s"${headSha.value}")
+TaskKey[Unit]("checkOnCommitDirty")       := check(version.value, s"${headSha.value}-${tstamp.value}")
+TaskKey[Unit]("checkOnTag")               := check(version.value, s"1.0.0")
+TaskKey[Unit]("checkOnTagDirty")          := check(version.value, s"1.0.0-${tstamp.value}")
+TaskKey[Unit]("checkOnTagAndCommit")      := check(version.value, s"1.0.0-1-${headSha.value}")
+TaskKey[Unit]("checkOnTagAndCommitDirty") := check(version.value, s"1.0.0-1-${headSha.value}-${tstamp.value}")
+
+TaskKey[Unit]("gitInitSetup") := {
+  "git init".!!(streams.value.log)
+  "git config user.email [email protected]".!!(streams.value.log)
+  "git config user.name dynver".!!(streams.value.log)
+}
+
+TaskKey[Unit]("gitAdd")    := "git add .".!!(streams.value.log)
+TaskKey[Unit]("gitCommit") := "git commit -am1".!!(streams.value.log)
+TaskKey[Unit]("gitTag")    := "git tag -a v1.0.0 -m1.0.0".!!(streams.value.log)
+
+TaskKey[Unit]("dirty") := {
+  import java.nio.file._, StandardOpenOption._
+  import scala.collection.JavaConverters._
+  Files.write(baseDirectory.value.toPath.resolve("f.txt"), Seq("1").asJava, CREATE, APPEND)
+}

src/sbt-test/dynver/custom-version-string-0/project/plugins.sbt

@@ -0,0 +1,5 @@
+sys.props.get("plugin.version") match {
+  case Some(x) => addSbtPlugin("com.dwijnand" % "sbt-dynver" % x)
+  case _       => sys.error("""|The system property 'plugin.version' is not defined.
+                               |Specify this property using the scriptedLaunchOpts -D.""".stripMargin)
+}

src/sbt-test/dynver/custom-version-string-0/test

@@ -0,0 +1,32 @@
+> checkNotAGitRepo
+
+> gitInitSetup
+> reload
+> checkNoCommits
+
+> dirty
+> gitAdd
+> gitCommit
+> reload
+> checkOnCommit
+
+> dirty
+> reload
+> checkOnCommitDirty
+
+> gitCommit
+> gitTag
+> reload
+> checkOnTag
+
+> dirty
+> reload
+> checkOnTagDirty
+
+> gitCommit
+> reload
+> checkOnTagAndCommit
+
+> dirty
+> reload
+> checkOnTagAndCommitDirty