Update documentation.

Author: DanielRose

docs/configuration.md

@@ -32,6 +32,7 @@ next-version: 1.0
 assembly-versioning-scheme: MajorMinorPatch
 assembly-informational-format: '{InformationalVersion}'
 mode: ContinuousDelivery
+increment: Inherit
 continuous-delivery-fallback-tag: ci
 tag-prefix: '[vV]'
 major-version-bump-message: '\+semver:\s?(breaking|major)'
@@ -70,6 +71,11 @@ value of the `AssemblyInformationalVersion` attribute. Default set to
 Sets the `mode` of how GitVersion should create a new version. Read more at
 [versioning mode](/reference/versioning-mode.md).
 
+### increment
+The part of the SemVer to increment when GitVersion detects it needs to be increased, such as for commits after a tag: `Major`, `Minor`, `Patch`, `None`.
+
+The special value `Inherit` means that GitVersion should find the parent branch (i.e. the branch where the current branch was branched from), and use its values for [increment](#increment), [prevent-increment-of-merged-branch-version](#prevent-increment-of-merged-branch-version) and [is-develop](#is-develop).
+
 ### continuous-delivery-fallback-tag
 When using `mode: ContinuousDeployment`, the value specified in
 `continuous-delivery-fallback-tag` will be used as the pre-release tag for
@@ -246,8 +252,7 @@ of `alpha.foo` with the value of `alpha.{BranchName}`.
 **Note:** To clear a default use an empty string: `tag: ''`
 
 ### increment
-The part of the SemVer to increment when GitVersion detects it needs to be (i.e
-commit after a tag)
+Same as for the [global configuration, explained above](#increment).
 
 ### prevent-increment-of-merged-branch-version
 When `release-2.0.0` is merged into master, we want master to build `2.0.0`. If

docs/more-info/version-sources.md

@@ -1,5 +1,5 @@
 # Version Sources
-GitVersion has a two step process for calculating the version number, the first is to calculate the base version which is used to then calculate what the next version should be.
+GitVersion has a two step process for calculating the version number. First it calculates the base version, which is then used to calculate what the next version should be.
 
 The logic of GitVersion is something like this:
 
@@ -8,26 +8,38 @@ The logic of GitVersion is something like this:
    - No: continue
  - Calculate the base version (highest version from all the sources)
  - Increment version if needed based on branch config
- - Calculate the build metadata (everything after the +) and append to the calcuated version
+ - Calculate the build metadata (everything after the +) and append to the calculated version
 
 ## Version Sources
-### Highest Accessible Tag
-GitVersion will find all tags on the current branch and return the highest one.
+### Tag name
+Returns the version numbers extracted from the current branch's tags.
 
 Will increment: true
 
 ### Version in branch name
-If the branch has a version in it, then that version will be returned.
+Returns the version number from the branch's name.
 
 Will increment: false
 
 ### Merge message
-If a branch with a version number in it is merged into the current branch, that version number will be used.
+Returns the version number of any branch (with a version number in its name) merged into the current branch.
 
-Will increment: false
+Will increment: depends on the value of `prevent-increment-of-merged-branch-version`
 
 ### GitVersion.yml
-If the `next-version` property is specified in the config file, it will be used as a version source.
+Returns the value of the `next-version` property in the config file.
+
+Will increment: false
+
+### Develop branch
+For the develop branch, i.e. marked with `is-develop: true`
+- Returns the version number extracted from any child release-branches, i.e. those marked with `is-release-branch: true`
+- Returns the version number of any tags on the master branch
+
+Will increment: true 
+
+### Fallback
+Returns the version number `0.1.0`.
 
 Will increment: false