[Libguestfs] [PATCH] fish: edit: write to the real file name

[Pino Toscano]

When saving, resolve the path of the file being edited and use that as
real target to write to. Otherwise, if the file name is a symlink then
it will be replaced by a regular file with the new content, leaving the
old file untouched.

Extend test-edit.sh to check for this situation.
---
 fish/file-edit.c  | 15 ++++++++++++++-
 fish/test-edit.sh | 12 +++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/fish/file-edit.c b/fish/file-edit.c
index e6d25f5..dd2272b 100644
--- a/fish/file-edit.c
+++ b/fish/file-edit.c
@@ -216,11 +216,24 @@ do_download (guestfs_h *g, const char *filename, char **tempfile)
 }
 
 static int
-do_upload (guestfs_h *g, const char *filename, const char *tempfile,
+do_upload (guestfs_h *g, const char *fn, const char *tempfile,
            const char *backup_extension)
 {
+  CLEANUP_FREE char *filename = NULL;
   CLEANUP_FREE char *newname = NULL;
 
+  /* Resolve the file name and write to the actual target, since
+   * that is the file it was opened earlier; otherwise, if it is
+   * a symlink it will be overwritten by a regular file with the
+   * new content.
+   *
+   * Theoretically realpath should work, but just check again
+   * to be safe.
+   */
+  filename = guestfs_realpath (g, fn);
+  if (filename == NULL)
+    return -1;
+
   /* Upload to a new file in the same directory, so if it fails we
    * don't end up with a partially written file.  Give the new file
    * a completely random name so we have only a tiny chance of
diff --git a/fish/test-edit.sh b/fish/test-edit.sh
index 34bfc9d..9d7ab9d 100755
--- a/fish/test-edit.sh
+++ b/fish/test-edit.sh
@@ -43,6 +43,12 @@ cat /file.txt
 stat /file.txt | grep mode:
 stat /file.txt | grep uid:
 stat /file.txt | grep gid:
+echo ==========
+write /file-2.txt "symlink test\n"
+ln-s /file-2.txt /symlink-2.txt
+edit /symlink-2.txt
+is-symlink /symlink-2.txt
+cat /symlink-2.txt
 EOF
 )
 
@@ -51,7 +57,11 @@ second line of text
 
 mode: 33152
 uid: 10
-gid: 11" ]; then
+gid: 11
+==========
+true
+symlink test
+second line of text" ]; then
     echo "$0: error: output of guestfish after edit command did not match expected output"
     echo "$output"
     exit 1
-- 
1.9.3