Found some more information on the song. Susanne

[1977:] This is the story of 200 men raised by the Lady of Moy for the Jacobite Rebellion in 1745. "They may be led by a woman," she said, "but they will not fight like women on the field." and appointed MacGillivray of Drumglass to lead them in battle. (Notes 'The Whistlebinkies')

[1988:] It is well known [...] that [James Hogg] passed off his own Donald Macgillavry as a relic of outstanding merit and undoubted authenticity [...]. Donald Macgillavry was published in the first series of the 'Relics' with a highly appreciative note. 'This', proclaimed Hogg, 'is one of the best songs that ever was made...a capital old song, and very popular'. He then proceeded upon an inquiry, as solemn as it was specious, into the historical background, unearthing several apparently genuine Macgillavrys - John M'Gillavry, executed at Preston in 1716, a Colonel M'Gillavry of the MacIntosh regiment in the '45 - suggesting that 'a bard connected with that associated clan may have written it'. But the note is designed to do more than put a gloss of authenticity upon the song. Its delightful wrong-headedness seems intended (as do various of the other notes in the 'Relics') as a skit on the unsmiling pedantry apt then as now to afflict popular-song studies. Its author was, after all, one of the most masterly parodists in the country:
"The Clan- Macgillavry is only a subordinate one, so that the name seems taken to represent the whole of the Scottish clans by a comical patronymic, that could not give offence to anyone, nor yet render any clan particularly obnoxious to the other party, by the song being sung in mixed assemblies. It may, however, have been written in allusion to that particular clan, small as it was, as we see Macgillavry of Drumglass mentioned in some copies of the Chevalier's Muster-Roll."
Hogg may simply have wanted to make his own contribution to what was very much a living tradition. It is not impossible, however, that a deeper game was afoot and that the Shepherd, well aware that Donald Macgillavry was one of his best pieces, something a reviewer of the 'Relics' was almost bound to notice, may have falsified its credentials in this way in order to ensnare the distinguished critic Francis Jeffrey. [...] If Donald MacGillavry was indeed a literary ambush, Jeffrey walked right into it. In the 1831 edition of his 'Songs', Hogg jubilantly recorded this famous victory. The piece had been
"originally published in the Jacobite Relics, without any notice of its being an original composition; an ommission which entrapped the Edinburgh Review into a high but unintentional compliment to the author. After reviewing the Relics in a style of most determined animosity, and protesting over and over again that I was devoid of all taste and discrimination, the tirade concluded in these terms: 'That we may not close this article without a specimen of the good songs which the book contains, we shall select the one which, for sly, characteristic Scotch humour, seems to us the best, though we doubt if any of our English readers will relish it'. The opportunity of retaliating upon the reviewer's want of sagacity was too tempting to be lost; and the authorship of the song was immediately avowed in a letter to the Editor of Blackwood's Magazine. ''After all', said this avowal, 'between ourselves, Donald M'Gillavry, which he has selected as the best specimen of the true old Jacobite song, and as remarkably above his fellows for 'sly, characteristic Scotch humour', is no other than a trifle of my own, which I put in to fill up a page.'"
Jeffrey was not mistaken in one respect, however. Donald Macgillavry is one of the best things in the collection, set to a lilting 6/8 in a minor key ideally suited to the repetition and word-play packed into the stanzas, and issuing an exuberant summons to resentful Gaeldom to deliver the nation from the thraldom of Whiggery. The hero is one of the legion of Comic Gaels and has various conventional features; but Hogg treats him sympathetically, identifying with him in a way unthinkable a generation before. His Highlandman is not a clownish barbarian, but a formidable character with a decisive political role [...].
Successive verses elaborate the pattern established in the first. The initial four lines enlarge upon the Highlandman's fury, and then he is invoked in various forms, as a weaver, tailor, cobbler, and so on, and this takes up the rest of the octave [...]. This wealth of trade- simile does not exhaust Hogg's resources. The injustices suffered by the protean hero are transformed by the same profusely inventive intelligence. Donald's grievance is the traditional Jacobite one against 'Cess and Press, and Presbytery'. But these prosaic concepts are translated in four brilliantly alliterative lines into fresh and highly concrete terms [...].
Hogg summarises a world of abstract social and political concept - all the inequalities and injustice of the mercantile civilisation of Whig Scotland - by means of a fecund supply of images drawn, ironically, from commerce itself. This in part is what gives the song that energy which Jeffrey mistook for authenticity. One of the sources of its excellence lies in the balance struck between the comic impulse of the convention and the seriousness of the theme. Another lies in its deft interplay with the tune.
The air is heptachordal in the Aeolian mode with a phrase pattern which would seem to indicate a triplet- and- refrain type text to coincide with its apparently tri- partite organisation, although it is actually binary in form. Hogg partially satisfies this impulse with refrain lines at the middle and end of his stanza, and in the third verse fulfils it almost exactly with the near-rhymes 'roguery, beggery, Whiggery'; but elsewhere he carefully avoids establishing it as the dominant pattern. The melody itself is highly organised and economical, with a haunting motif based on the interplay of tonic, dominant and flattened seventh. These intervals are strongly emphasised and Hogg takes advantage of their almost incantatory quality to invoke the Highlandman in appropriate form. The resulting texture of balance and contrast reveals him as a sensitive craftsman responsive to the underlying character of the melody and subtly reflecting its tensions in its lines. (William Donaldson, The Jacobite Song. Political myth and national identity, 99ff.)