diff --git a/src/PkgTemplates.jl b/src/PkgTemplates.jl
index 8c9ae6d8..29d06f22 100644
--- a/src/PkgTemplates.jl
+++ b/src/PkgTemplates.jl
@@ -38,7 +38,8 @@ export
     SrcDir,
     TagBot,
     Tests,
-    TravisCI
+    TravisCI,
+    fixup
 
 """
 Plugins are PkgTemplates' source of customization and extensibility.
@@ -48,10 +49,19 @@ When implementing a new plugin, subtype this type to have full control over its
 """
 abstract type Plugin end
 
+"""
+    isfixable(::Plugin, pkg_dir) -> Bool
+
+Determines whether or not the plugin can be updated on an existing project via
+[`fixup`](@ref).
+"""
+isfixable(::Plugin, pkg_dir) = false
+
 include("template.jl")
 include("plugin.jl")
 include("show.jl")
 include("interactive.jl")
+include("fixup.jl")
 include("deprecated.jl")
 
 # Run some function with a project activated at the given path.
diff --git a/src/fixup.jl b/src/fixup.jl
new file mode 100644
index 00000000..78e6dfbb
--- /dev/null
+++ b/src/fixup.jl
@@ -0,0 +1,15 @@
+function fixup(tpl::Template, pkg_dir)
+    pkg_dir = realpath(pkg_dir)
+    ispath(pkg_dir) || throw(ArgumentError("Not a directory."))
+    isdir(joinpath(pkg_dir, "src")) || throw(ArgumentError("No `src/` directory."))
+
+    fixable = filter(p -> isfixable(p, pkg_dir), tpl.plugins)
+    foreach((prehook, hook, posthook)) do h
+        @info "Running $(nameof(h))s"
+        foreach(sort(fixable; by=p -> priority(p, h), rev=true)) do p
+            h(p, tpl, pkg_dir)
+        end
+    end
+    @info "Fixed up package at $pkg_dir"
+    # TODO: some magic to add badges to an existing Readme?!
+end
diff --git a/src/plugin.jl b/src/plugin.jl
index c6c6eed4..ba2a59a7 100644
--- a/src/plugin.jl
+++ b/src/plugin.jl
@@ -210,6 +210,17 @@ This function **must** be implemented.
 """
 function destination end
 
+"""
+    isfixable(p::FilePlugin) -> Bool
+
+Determines whether or not [`fixup`](@ref) should update the files created by `p`.
+
+By default, returns `true` if the [`destination(p)`](@ref) file does not exist.
+Subtype of [`FilePlugin`](@ref) should implement their own method if they require
+different behaviour.
+"""
+isfixable(p::FilePlugin, pkg_dir) = !isfile(joinpath(pkg_dir, destination(p)))
+
 """
     Badge(hover::AbstractString, image::AbstractString, link::AbstractString)
 
diff --git a/src/plugins/documenter.jl b/src/plugins/documenter.jl
index 2f321659..359a6660 100644
--- a/src/plugins/documenter.jl
+++ b/src/plugins/documenter.jl
@@ -161,6 +161,9 @@ function validate(p::Documenter{T}, t::Template) where T <: YesDeploy
     end
 end
 
+# Do not edit existing docs.
+isfixable(::Documenter, pkg_dir) = !isdir(joinpath(pkg_dir, "docs"))
+
 function hook(p::Documenter, t::Template, pkg_dir::AbstractString)
     pkg = basename(pkg_dir)
     docs_dir = joinpath(pkg_dir, "docs")
diff --git a/src/plugins/git.jl b/src/plugins/git.jl
index 5b235d56..be15f781 100644
--- a/src/plugins/git.jl
+++ b/src/plugins/git.jl
@@ -54,6 +54,16 @@ function validate(p::Git, t::Template)
     end
 end
 
+# fixup only if pkg_dir not a git repo
+function isfixable(::Git, pkg_dir)
+    try
+        r = GitRepo(pkg_dir)
+        return !isa(r, GitRepo)
+    catch
+        return true
+    end
+end
+
 # Set up the Git repository.
 function prehook(p::Git, t::Template, pkg_dir::AbstractString)
     LibGit2.with(LibGit2.init(pkg_dir)) do repo
diff --git a/src/plugins/license.jl b/src/plugins/license.jl
index 656fb16b..e5bbf248 100644
--- a/src/plugins/license.jl
+++ b/src/plugins/license.jl
@@ -40,6 +40,10 @@ view(::License, t::Template, ::AbstractString) = Dict(
     "YEAR" => year(today()),
 )
 
+function isfixable(::License, pkg_dir)
+    return !any(isfile, joinpath.(pkg_dir, ("LICENSE", "LICENSE.md")))
+end
+
 function prompt(::Type{License}, ::Type, ::Val{:name})
     options = readdir(default_file("licenses"))
     # Move MIT to the top.
diff --git a/src/plugins/project_file.jl b/src/plugins/project_file.jl
index 28efd583..ff78b892 100644
--- a/src/plugins/project_file.jl
+++ b/src/plugins/project_file.jl
@@ -15,7 +15,9 @@ priority(::ProjectFile, ::typeof(hook)) = typemax(Int) - 5
 
 function hook(p::ProjectFile, t::Template, pkg_dir::AbstractString)
     toml = Dict(
-        "name" => basename(pkg_dir),
+        "name" => let pkg = basename(pkg_dir)
+            endswith(pkg, ".jl") ? pkg[1:end-3] : pkg
+        end,
         "uuid" => string(uuid4()),
         "authors" => t.authors,
         "version" => string(p.version),
@@ -38,3 +40,7 @@ function compat_version(v::VersionNumber)
         "$(v.major).$(v.minor).$(v.patch)"
     end
 end
+
+function isfixable(::ProjectFile, pkg_dir)
+    return !any(isfile, joinpath.(pkg_dir, ("Project.toml", "JuliaProject.toml")))
+end
diff --git a/src/plugins/src_dir.jl b/src/plugins/src_dir.jl
index e6004e08..41fb2a57 100644
--- a/src/plugins/src_dir.jl
+++ b/src/plugins/src_dir.jl
@@ -29,3 +29,6 @@ view(::SrcDir, ::Template, pkg::AbstractString) = Dict("PKG" => pkg)
 function prehook(p::SrcDir, t::Template, pkg_dir::AbstractString)
     p.destination = joinpath("src", basename(pkg_dir) * ".jl")
 end
+
+# TODO: should this return `true` if `src/` exists but `src/pkg_name.jl` doesn't?
+isfixable(p::SrcDir, pkg_dir) = false