Add --no-git flag to gen all

The flag skips steps whichr require a git checkout, currently only the
changelog generator.

type: added

bin/gen/src/changelog.rs

@@ -7,7 +7,9 @@ pub(crate) struct Changelog {
 impl Changelog {
   #[throws]
   pub(crate) fn new(project: &Project) -> Self {
-    let mut current = project.repo.head()?.peel_to_commit()?;
+    let repo = project.repo()?;
+
+    let mut current = repo.head()?.peel_to_commit()?;
 
     let mut entries = Vec::new();
 
@@ -24,7 +26,7 @@ impl Changelog {
         let manifest_bytes = current
           .tree()?
           .get_path("Cargo.toml".as_ref())?
-          .to_object(&project.repo)?
+          .to_object(&repo)?
           .as_blob()
           .unwrap()
           .content()

bin/gen/src/error.rs

@@ -68,7 +68,7 @@ pub(crate) enum Error {
   Git { source: git2::Error },
   #[snafu(display("Regex compilation error: {}", source))]
   Regex { source: regex::Error },
-  #[snafu(display("Failed to find repository from `{}`: {}", start_dir.display(), source))]
+  #[snafu(display("Failed to find Git repository from `{}`: {}", start_dir.display(), source))]
   RepositoryDiscover {
     start_dir: PathBuf,
     source: git2::Error,

bin/gen/src/project.rs

@@ -1,7 +1,6 @@
 use crate::common::*;
 
 pub(crate) struct Project {
-  pub(crate) repo: Repository,
   pub(crate) root: PathBuf,
   pub(crate) config: Config,
   pub(crate) bin: Bin,
@@ -11,16 +10,7 @@ pub(crate) struct Project {
 impl Project {
   #[throws]
   pub(crate) fn load(options: &Options) -> Self {
-    let start_dir = env::current_dir().context(error::CurrentDir)?;
-
-    let repo = Repository::discover(&start_dir).context(error::RepositoryDiscover { start_dir })?;
-
-    let root = repo
-      .workdir()
-      .ok_or_else(|| Error::Workdir {
-        repo: repo.path().to_owned(),
-      })?
-      .to_owned();
+    let root = env::current_dir().context(error::CurrentDir)?;
 
     let config = Config::load(&root)?;
 
@@ -49,7 +39,6 @@ impl Project {
       executable: options.bin.clone(),
       bin,
       config,
-      repo,
       root,
     }
   }
@@ -64,4 +53,11 @@ impl Project {
 
     gen
   }
+
+  #[throws]
+  pub(crate) fn repo(&self) -> Repository {
+    Repository::discover(&self.root).context(error::RepositoryDiscover {
+      start_dir: &self.root,
+    })?
+  }
 }

bin/gen/src/subcommand.rs

@@ -3,7 +3,14 @@ use crate::common::*;
 #[derive(StructOpt)]
 pub(crate) enum Subcommand {
   #[structopt(about("Update all generated docs"))]
-  All,
+  All {
+    #[structopt(
+      long = "no-git",
+      help = "Skip generated outputs that require a Git repository. Currently this only includes \
+              the changelog."
+    )]
+    no_git: bool,
+  },
   #[structopt(about("Generate book"))]
   Book,
   #[structopt(about("Generate the changelog"))]
@@ -73,13 +80,15 @@ impl Subcommand {
       Self::Book => Self::book(&project)?,
       Self::Man => Self::man(&project)?,
       Self::Diff => Self::diff(&project)?,
-      Self::All => Self::all(&project)?,
+      Self::All { no_git } => Self::all(&project, no_git)?,
     }
   }
 
   #[throws]
-  pub(crate) fn all(project: &Project) {
-    Self::changelog(&project)?;
+  pub(crate) fn all(project: &Project, no_git: bool) {
+    if !no_git {
+      Self::changelog(&project)?;
+    }
     Self::completion_scripts(&project)?;
     Self::readme(&project)?;
     Self::book(&project)?;
@@ -131,7 +140,9 @@ impl Subcommand {
 
     gen(HEAD)?;
 
-    let head = project.repo.head()?;
+    let repo = project.repo()?;
+
+    let head = repo.head()?;
 
     let head_commit = head.peel_to_commit()?;