Add support for running Kakoune with redirected stdin

Will read to a *stdin* fifo buffer

src/buffer_utils.cc

@@ -1,5 +1,7 @@
 #include "buffer_utils.hh"
 
+#include "event_manager.hh"
+
 namespace Kakoune
 {
 
@@ -20,4 +22,37 @@ CharCount get_column(const Buffer& buffer,
     return col;
 }
 
+Buffer* create_fifo_buffer(String name, int fd)
+{
+    Buffer* buffer = new Buffer(std::move(name), Buffer::Flags::Fifo | Buffer::Flags::NoUndo);
+
+    auto watcher = new FDWatcher(fd, [buffer](FDWatcher& watcher) {
+        constexpr size_t buffer_size = 1024 * 16;
+        char data[buffer_size];
+        ssize_t count = read(watcher.fd(), data, buffer_size);
+        buffer->insert(buffer->end()-1, count > 0 ? String(data, data+count)
+                                                  : "*** kak: fifo closed ***\n");
+        if (count <= 0)
+        {
+            kak_assert(buffer->flags() & Buffer::Flags::Fifo);
+            buffer->flags() &= ~Buffer::Flags::Fifo;
+            buffer->flags() &= ~Buffer::Flags::NoUndo;
+            close(watcher.fd());
+            delete &watcher;
+        }
+    });
+
+    buffer->hooks().add_hook("BufClose", "",
+        [buffer, watcher](const String&, const Context&) {
+            // Check if fifo is still alive, else watcher is already dead
+            if (buffer->flags() & Buffer::Flags::Fifo)
+            {
+                close(watcher->fd());
+                delete watcher;
+            }
+        });
+
+    return buffer;
+}
+
 }

src/buffer_utils.hh

@@ -41,6 +41,8 @@ inline void avoid_eol(const Buffer& buffer, Selection& sel)
 CharCount get_column(const Buffer& buffer,
                      CharCount tabstop, BufferCoord coord);
 
+Buffer* create_fifo_buffer(String name, int fd);
+
 }
 
 #endif // buffer_utils_hh_INCLUDED

src/commands.cc

@@ -2,6 +2,7 @@
 
 #include "buffer.hh"
 #include "buffer_manager.hh"
+#include "buffer_utils.hh"
 #include "client.hh"
 #include "client_manager.hh"
 #include "color_registry.hh"
@@ -45,7 +46,7 @@ Buffer* open_or_create(const String& filename, Context& context)
     return buffer;
 }
 
-Buffer* open_fifo(const String& name , const String& filename, Context& context)
+Buffer* open_fifo(const String& name , const String& filename)
 {
     int fd = open(parse_filename(filename).c_str(), O_RDONLY);
     fcntl(fd, F_SETFD, FD_CLOEXEC);
@@ -54,35 +55,7 @@ Buffer* open_fifo(const String& name , const String& filename, Context& context)
 
     BufferManager::instance().delete_buffer_if_exists(name);
 
-    Buffer* buffer = new Buffer(name, Buffer::Flags::Fifo | Buffer::Flags::NoUndo);
-
-    auto watcher = new FDWatcher(fd, [buffer](FDWatcher& watcher) {
-        constexpr size_t buffer_size = 1024 * 16;
-        char data[buffer_size];
-        ssize_t count = read(watcher.fd(), data, buffer_size);
-        buffer->insert(buffer->end()-1, count > 0 ? String(data, data+count)
-                                                  : "*** kak: fifo closed ***\n");
-        if (count <= 0)
-        {
-            kak_assert(buffer->flags() & Buffer::Flags::Fifo);
-            buffer->flags() &= ~Buffer::Flags::Fifo;
-            buffer->flags() &= ~Buffer::Flags::NoUndo;
-            close(watcher.fd());
-            delete &watcher;
-        }
-    });
-
-    buffer->hooks().add_hook("BufClose", "",
-        [buffer, watcher](const String&, const Context&) {
-            // Check if fifo is still alive, else watcher is already dead
-            if (buffer->flags() & Buffer::Flags::Fifo)
-            {
-                close(watcher->fd());
-                delete watcher;
-            }
-        });
-
-    return buffer;
+    return create_fifo_buffer(std::move(name), fd);
 }
 
 const PerArgumentCommandCompleter filename_completer({
@@ -138,7 +111,7 @@ void edit(const ParametersParser& parser, Context& context)
             buffer = new Buffer(name, Buffer::Flags::None);
         }
         else if (parser.has_option("fifo"))
-            buffer = open_fifo(name, parser.option_value("fifo"), context);
+            buffer = open_fifo(name, parser.option_value("fifo"));
         else
             buffer = open_or_create(name, context);
     }

src/main.cc

@@ -30,6 +30,10 @@
 #include <locale>
 #include <signal.h>
 
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
 using namespace Kakoune;
 
 void run_unit_tests();
@@ -192,6 +196,19 @@ void create_local_client(const String& init_command)
         }
     };
 
+    if (not isatty(1))
+        throw runtime_error("stdout is not a tty");
+
+    if (not isatty(0))
+    {
+        // move stdin to another fd, and restore tty as stdin
+        int fd = dup(0);
+        int tty = open("/dev/tty", O_RDONLY);
+        dup2(tty, 0);
+        close(tty);
+        create_fifo_buffer("*stdin*", fd);
+    }
+
     UserInterface* ui = new LocalNCursesUI{};
     static Client* client = ClientManager::instance().create_client(
         std::unique_ptr<UserInterface>{ui}, get_env_vars(), init_command);