Merge pull request #1043 from xinslu/master

Added ability to specify target of build

Author: pkgw

docs/src/v2cli/build.md

@@ -18,6 +18,7 @@ tectonic -X build
   [--print]
   [--open]
   [--untrusted]
+  [--target NAME]
 ```
 
 #### Remarks
@@ -32,6 +33,10 @@ directory.
 
 #### Command-Line Options
 
+The `--target` option will only build the
+[output](../ref/tectonic-toml.md#output) with the specified name. If this option
+is not given, all outputs will be built.
+
 The `--keep-intermediates` option (or `-k` for short) will cause the engine to
 save intermediate files (such as `mydoc.aux` or `mydoc.bbl`) in the build output
 directory. By default, these files are stored in memory but not actually written

src/bin/tectonic/v2cli.rs

@@ -238,6 +238,10 @@ pub struct BuildCommand {
     /// Open built document using system handler
     #[structopt(long)]
     open: bool,
+
+    /// Specify a target to be used by the build
+    #[structopt(long, help = "Specify the target of the build.")]
+    target: Option<String>,
 }
 
 impl BuildCommand {
@@ -262,6 +266,12 @@ impl BuildCommand {
         setup_options.only_cached(self.only_cached);
 
         for output_name in doc.output_names() {
+            if let Some(out) = self.target.as_ref() {
+                if out != output_name {
+                    continue;
+                }
+            }
+
             let mut builder = doc.setup_session(output_name, &setup_options, status)?;
 
             builder